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 $43.61   6.782%   $46.5676   $46.57   $46.55   $46.60  
  Purchase #2 $220.45   7.765%   $237.5679   $237.57   $237.55   $237.60  
  Purchase #3 $93.59   9.552%   $102.5297   $102.53   $102.55   $102.50  
  Purchase #4 $143.47   10.564%   $158.6262   $158.63   $158.65   $158.60  
  Purchase #5 $112.59   6.137%   $119.4996   $119.50   $119.50   $119.50  
  Purchase #6 $71.65   13.204%   $81.1107   $81.11   $81.10   $81.10  
  Purchase #7 $162.79   13.531%   $184.8171   $184.82   $184.80   $184.80  
  7 purchase totals = $848.15       $930.7188   $930.73   $930.70   $930.70