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 $210.41   10.729%   $232.9849   $232.98   $233.00   $233.00  
  Purchase #2 $55.60   10.710%   $61.5548   $61.55   $61.55   $61.60  
  Purchase #3 $114.38   9.557%   $125.3113   $125.31   $125.30   $125.30  
  Purchase #4 $156.54   9.694%   $171.715   $171.72   $171.70   $171.70  
  Purchase #5 $216.48   8.828%   $235.5909   $235.59   $235.60   $235.60  
  Purchase #6 $8.71   11.591%   $9.7196   $9.72   $9.70   $9.70  
  Purchase #7 $126.53   3.802%   $131.3407   $131.34   $131.35   $131.30  
  7 purchase totals = $888.65       $968.2172   $968.21   $968.20   $968.20