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 $62.52   7.228%   $67.0389   $67.04   $67.05   $67.00  
  Purchase #2 $150.91   4.676%   $157.9666   $157.97   $157.95   $158.00  
  Purchase #3 $135.90   7.203%   $145.6889   $145.69   $145.70   $145.70  
  Purchase #4 $214.51   5.631%   $226.5891   $226.59   $226.60   $226.60  
  Purchase #5 $121.51   7.298%   $130.3778   $130.38   $130.40   $130.40  
  Purchase #6 $170.98   12.463%   $192.2892   $192.29   $192.30   $192.30  
  Purchase #7 $195.35   8.557%   $212.0661   $212.07   $212.05   $212.10  
  7 purchase totals = $1,051.68       $1,132.0166   $1,132.03   $1,132.05   $1,132.10