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 $194.65   3.283%   $201.0404   $201.04   $201.05   $201.00  
  Purchase #2 $99.68   8.419%   $108.0721   $108.07   $108.05   $108.10  
  Purchase #3 $183.71   9.194%   $200.6003   $200.60   $200.60   $200.60  
  Purchase #4 $40.30   3.297%   $41.6287   $41.63   $41.65   $41.60  
  Purchase #5 $24.84   5.753%   $26.269   $26.27   $26.25   $26.30  
  Purchase #6 $20.39   7.221%   $21.8624   $21.86   $21.85   $21.90  
  Purchase #7 $129.53   6.568%   $138.0375   $138.04   $138.05   $138.00  
  7 purchase totals = $693.10       $737.5104   $737.51   $737.50   $737.50