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 $210.75   11.527%   $235.0432   $235.04   $235.05   $235.00  
  Purchase #2 $153.68   6.147%   $163.1267   $163.13   $163.15   $163.10  
  Purchase #3 $101.71   13.603%   $115.5456   $115.55   $115.55   $115.50  
  Purchase #4 $95.92   9.251%   $104.7936   $104.79   $104.80   $104.80  
  Purchase #5 $95.26   10.871%   $105.6157   $105.62   $105.60   $105.60  
  Purchase #6 $218.38   6.424%   $232.4087   $232.41   $232.40   $232.40  
  Purchase #7 $10.85   8.635%   $11.7869   $11.79   $11.80   $11.80  
  7 purchase totals = $886.55       $968.3204   $968.33   $968.35   $968.20