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 $246.86   7.424%   $265.1869   $265.19   $265.20   $265.20  
  Purchase #2 $201.71   4.280%   $210.3432   $210.34   $210.35   $210.30  
  Purchase #3 $46.68   7.582%   $50.2193   $50.22   $50.20   $50.20  
  Purchase #4 $99.37   9.738%   $109.0467   $109.05   $109.05   $109.00  
  Purchase #5 $178.72   8.627%   $194.1382   $194.14   $194.15   $194.10  
  Purchase #6 $187.76   3.289%   $193.9354   $193.94   $193.95   $193.90  
  Purchase #7 $101.60   3.164%   $104.8146   $104.81   $104.80   $104.80  
  7 purchase totals = $1,062.70       $1,127.6843   $1,127.69   $1,127.70   $1,127.50