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 $46.77   11.127%   $51.9741   $51.97   $51.95   $52.00  
  Purchase #2 $141.35   13.279%   $160.1199   $160.12   $160.10   $160.10  
  Purchase #3 $76.52   10.775%   $84.765   $84.77   $84.75   $84.80  
  Purchase #4 $23.43   4.330%   $24.4445   $24.44   $24.45   $24.40  
  Purchase #5 $92.81   5.564%   $97.9739   $97.97   $97.95   $98.00  
  Purchase #6 $201.80   12.387%   $226.797   $226.80   $226.80   $226.80  
  Purchase #7 $97.69   9.536%   $107.0057   $107.01   $107.00   $107.00  
  7 purchase totals = $680.37       $753.0801   $753.08   $753.00   $753.10