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 $152.85   7.212%   $163.8735   $163.87   $163.85   $163.90  
  Purchase #2 $230.57   13.793%   $262.3725   $262.37   $262.35   $262.40  
  Purchase #3 $84.87   12.405%   $95.3981   $95.40   $95.40   $95.40  
  Purchase #4 $105.59   4.632%   $110.4809   $110.48   $110.50   $110.50  
  Purchase #5 $229.74   10.843%   $254.6507   $254.65   $254.65   $254.70  
  Purchase #6 $167.67   3.683%   $173.8453   $173.85   $173.85   $173.80  
  Purchase #7 $77.46   8.425%   $83.986   $83.99   $84.00   $84.00  
  7 purchase totals = $1,048.75       $1,144.6070   $1,144.61   $1,144.60   $1,144.70