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 $77.46   10.683%   $85.7351   $85.74   $85.75   $85.70  
  Purchase #2 $95.39   10.362%   $105.2743   $105.27   $105.25   $105.30  
  Purchase #3 $43.91   7.498%   $47.2024   $47.20   $47.20   $47.20  
  Purchase #4 $128.48   3.699%   $133.2325   $133.23   $133.25   $133.20  
  Purchase #5 $243.62   13.562%   $276.6597   $276.66   $276.65   $276.70  
  Purchase #6 $219.33   9.222%   $239.5566   $239.56   $239.55   $239.60  
  Purchase #7 $79.89   10.472%   $88.2561   $88.26   $88.25   $88.30  
  7 purchase totals = $888.08       $975.9167   $975.92   $975.90   $976.00