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 $176.39   10.208%   $194.3959   $194.40   $194.40   $194.40  
  Purchase #2 $88.73   13.323%   $100.5515   $100.55   $100.55   $100.60  
  Purchase #3 $209.43   11.194%   $232.8736   $232.87   $232.85   $232.90  
  Purchase #4 $152.63   3.163%   $157.4577   $157.46   $157.45   $157.50  
  Purchase #5 $122.83   7.431%   $131.9575   $131.96   $131.95   $132.00  
  Purchase #6 $166.52   10.656%   $184.2644   $184.26   $184.25   $184.30  
  Purchase #7 $46.71   11.185%   $51.9345   $51.93   $51.95   $51.90  
  7 purchase totals = $963.24       $1,053.4351   $1,053.43   $1,053.40   $1,053.60