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 $83.34   11.258%   $92.7224   $92.72   $92.70   $92.70  
  Purchase #2 $81.84   4.332%   $85.3853   $85.39   $85.40   $85.40  
  Purchase #3 $187.53   8.118%   $202.7537   $202.75   $202.75   $202.80  
  Purchase #4 $176.69   13.638%   $200.787   $200.79   $200.80   $200.80  
  Purchase #5 $36.61   12.371%   $41.139   $41.14   $41.15   $41.10  
  Purchase #6 $155.29   9.213%   $169.5969   $169.60   $169.60   $169.60  
  Purchase #7 $148.65   8.565%   $161.3819   $161.38   $161.40   $161.40  
  7 purchase totals = $869.95       $953.7662   $953.77   $953.80   $953.80