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 $38.48   13.368%   $43.624   $43.62   $43.60   $43.60  
  Purchase #2 $223.27   6.796%   $238.4434   $238.44   $238.45   $238.40  
  Purchase #3 $236.96   11.403%   $263.9805   $263.98   $264.00   $264.00  
  Purchase #4 $178.73   8.418%   $193.7755   $193.78   $193.80   $193.80  
  Purchase #5 $73.39   3.718%   $76.1186   $76.12   $76.10   $76.10  
  Purchase #6 $225.85   4.302%   $235.5661   $235.57   $235.55   $235.60  
  Purchase #7 $210.97   11.450%   $235.1261   $235.13   $235.15   $235.10  
  7 purchase totals = $1,187.65       $1,286.6342   $1,286.64   $1,286.65   $1,286.60