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 $197.84   8.843%   $215.335   $215.34   $215.35   $215.30  
  Purchase #2 $179.32   12.663%   $202.0273   $202.03   $202.05   $202.00  
  Purchase #3 $215.88   8.301%   $233.8002   $233.80   $233.80   $233.80  
  Purchase #4 $58.40   13.398%   $66.2244   $66.22   $66.20   $66.20  
  Purchase #5 $188.48   9.402%   $206.2009   $206.20   $206.20   $206.20  
  Purchase #6 $52.30   7.460%   $56.2016   $56.20   $56.20   $56.20  
  Purchase #7 $125.92   6.854%   $134.5506   $134.55   $134.55   $134.60  
  7 purchase totals = $1,018.14       $1,114.3400   $1,114.34   $1,114.35   $1,114.30