Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $118.76   11.164%   $132.0184   $132.02   $132.00   $132.00  
  Purchase #2 $223.99   10.132%   $246.6847   $246.68   $246.70   $246.70  
  Purchase #3 $244.84   10.160%   $269.7157   $269.72   $269.70   $269.70  
  Purchase #4 $234.55   12.216%   $263.2026   $263.20   $263.20   $263.20  
  Purchase #5 $111.67   4.596%   $116.8024   $116.80   $116.80   $116.80  
  Purchase #6 $171.27   12.687%   $192.999   $193.00   $193.00   $193.00  
  Purchase #7 $249.60   7.778%   $269.0139   $269.01   $269.00   $269.00  
  7 purchase totals = $1,354.68       $1,490.4367   $1,490.43   $1,490.40   $1,490.40