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 $86.50   12.427%   $97.2494   $97.25   $97.25   $97.20  
  Purchase #2 $210.43   5.436%   $221.869   $221.87   $221.85   $221.90  
  Purchase #3 $202.92   12.553%   $228.3925   $228.39   $228.40   $228.40  
  Purchase #4 $50.53   10.133%   $55.6502   $55.65   $55.65   $55.70  
  Purchase #5 $23.92   10.158%   $26.3498   $26.35   $26.35   $26.30  
  Purchase #6 $143.48   12.638%   $161.613   $161.61   $161.60   $161.60  
  Purchase #7 $244.45   3.849%   $253.8589   $253.86   $253.85   $253.90  
  7 purchase totals = $962.23       $1,044.9828   $1,044.98   $1,044.95   $1,045.00