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 $59.27   5.785%   $62.6988   $62.70   $62.70   $62.70  
  Purchase #2 $207.58   12.317%   $233.1476   $233.15   $233.15   $233.10  
  Purchase #3 $10.27   5.568%   $10.8418   $10.84   $10.85   $10.80  
  Purchase #4 $52.97   4.688%   $55.4532   $55.45   $55.45   $55.50  
  Purchase #5 $210.74   5.751%   $222.8597   $222.86   $222.85   $222.90  
  Purchase #6 $68.95   11.785%   $77.0758   $77.08   $77.10   $77.10  
  Purchase #7 $97.95   4.728%   $102.5811   $102.58   $102.60   $102.60  
  7 purchase totals = $707.73       $764.6580   $764.66   $764.70   $764.70