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 $195.55   10.770%   $216.6107   $216.61   $216.60   $216.60  
  Purchase #2 $140.65   12.703%   $158.5168   $158.52   $158.50   $158.50  
  Purchase #3 $169.88   4.580%   $177.6605   $177.66   $177.65   $177.70  
  Purchase #4 $162.97   9.433%   $178.343   $178.34   $178.35   $178.30  
  Purchase #5 $55.27   11.290%   $61.51   $61.51   $61.50   $61.50  
  Purchase #6 $145.57   9.308%   $159.1197   $159.12   $159.10   $159.10  
  Purchase #7 $178.43   13.763%   $202.9873   $202.99   $203.00   $203.00  
  7 purchase totals = $1,048.32       $1,154.7480   $1,154.75   $1,154.70   $1,154.70