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 $106.45   5.775%   $112.5975   $112.60   $112.60   $112.60  
  Purchase #2 $87.92   11.179%   $97.7486   $97.75   $97.75   $97.70  
  Purchase #3 $56.43   11.540%   $62.942   $62.94   $62.95   $62.90  
  Purchase #4 $74.44   4.167%   $77.5419   $77.54   $77.55   $77.50  
  Purchase #5 $131.31   5.752%   $138.863   $138.86   $138.85   $138.90  
  Purchase #6 $223.53   9.143%   $243.9673   $243.97   $243.95   $244.00  
  Purchase #7 $54.25   7.695%   $58.4245   $58.42   $58.40   $58.40  
  7 purchase totals = $734.33       $792.0848   $792.08   $792.05   $792.00