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 $208.89   4.491%   $218.2712   $218.27   $218.25   $218.30  
  Purchase #2 $232.81   5.381%   $245.3375   $245.34   $245.35   $245.30  
  Purchase #3 $9.43   6.122%   $10.0073   $10.01   $10.00   $10.00  
  Purchase #4 $233.48   13.399%   $264.764   $264.76   $264.75   $264.80  
  Purchase #5 $161.78   9.591%   $177.2963   $177.30   $177.30   $177.30  
  Purchase #6 $53.52   4.333%   $55.839   $55.84   $55.85   $55.80  
  Purchase #7 $153.49   6.110%   $162.8682   $162.87   $162.85   $162.90  
  7 purchase totals = $1,053.40       $1,134.3835   $1,134.39   $1,134.35   $1,134.40