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 $55.28   12.186%   $62.0164   $62.02   $62.00   $62.00  
  Purchase #2 $91.65   3.166%   $94.5516   $94.55   $94.55   $94.60  
  Purchase #3 $137.98   11.864%   $154.3499   $154.35   $154.35   $154.30  
  Purchase #4 $179.94   4.377%   $187.816   $187.82   $187.80   $187.80  
  Purchase #5 $17.73   7.413%   $19.0443   $19.04   $19.05   $19.00  
  Purchase #6 $67.98   11.289%   $75.6543   $75.65   $75.65   $75.70  
  Purchase #7 $149.72   8.604%   $162.6019   $162.60   $162.60   $162.60  
  7 purchase totals = $700.28       $756.0344   $756.03   $756.00   $756.00