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 $92.60   4.732%   $96.9818   $96.98   $97.00   $97.00  
  Purchase #2 $155.42   12.746%   $175.2298   $175.23   $175.25   $175.20  
  Purchase #3 $17.27   3.602%   $17.8921   $17.89   $17.90   $17.90  
  Purchase #4 $55.59   5.610%   $58.7086   $58.71   $58.70   $58.70  
  Purchase #5 $198.70   7.183%   $212.9726   $212.97   $212.95   $213.00  
  Purchase #6 $244.87   11.360%   $272.6872   $272.69   $272.70   $272.70  
  Purchase #7 $159.35   12.713%   $179.6082   $179.61   $179.60   $179.60  
  7 purchase totals = $923.80       $1,014.0803   $1,014.08   $1,014.10   $1,014.10