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 $205.89   13.774%   $234.2493   $234.25   $234.25   $234.20  
  Purchase #2 $122.30   12.579%   $137.6841   $137.68   $137.70   $137.70  
  Purchase #3 $150.46   7.729%   $162.0891   $162.09   $162.10   $162.10  
  Purchase #4 $44.67   7.643%   $48.0841   $48.08   $48.10   $48.10  
  Purchase #5 $247.42   11.458%   $275.7694   $275.77   $275.75   $275.80  
  Purchase #6 $139.52   7.403%   $149.8487   $149.85   $149.85   $149.80  
  Purchase #7 $40.85   11.248%   $45.4448   $45.44   $45.45   $45.40  
  7 purchase totals = $951.11       $1,053.1695   $1,053.16   $1,053.20   $1,053.10