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 $53.33   4.587%   $55.7762   $55.78   $55.80   $55.80  
  Purchase #2 $195.82   5.355%   $206.3062   $206.31   $206.30   $206.30  
  Purchase #3 $193.51   5.676%   $204.4936   $204.49   $204.50   $204.50  
  Purchase #4 $60.82   7.793%   $65.5597   $65.56   $65.55   $65.60  
  Purchase #5 $235.75   3.737%   $244.56   $244.56   $244.55   $244.60  
  Purchase #6 $70.50   8.660%   $76.6053   $76.61   $76.60   $76.60  
  Purchase #7 $184.64   13.543%   $209.6458   $209.65   $209.65   $209.60  
  7 purchase totals = $994.37       $1,062.9468   $1,062.96   $1,062.95   $1,063.00