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 $216.32   8.267%   $234.2032   $234.20   $234.20   $234.20  
  Purchase #2 $91.26   11.219%   $101.4985   $101.50   $101.50   $101.50  
  Purchase #3 $93.88   11.423%   $104.6039   $104.60   $104.60   $104.60  
  Purchase #4 $183.85   12.251%   $206.3735   $206.37   $206.35   $206.40  
  Purchase #5 $224.80   7.587%   $241.8556   $241.86   $241.85   $241.90  
  Purchase #6 $24.84   8.678%   $26.9956   $27.00   $27.00   $27.00  
  Purchase #7 $138.84   9.802%   $152.4491   $152.45   $152.45   $152.40  
  7 purchase totals = $973.79       $1,067.9794   $1,067.98   $1,067.95   $1,068.00