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 $83.30   12.792%   $93.9557   $93.96   $93.95   $94.00  
  Purchase #2 $212.97   10.406%   $235.1317   $235.13   $235.15   $235.10  
  Purchase #3 $145.52   10.121%   $160.2481   $160.25   $160.25   $160.20  
  Purchase #4 $33.51   11.514%   $37.3683   $37.37   $37.35   $37.40  
  Purchase #5 $154.79   12.348%   $173.9035   $173.90   $173.90   $173.90  
  Purchase #6 $48.77   10.767%   $54.0211   $54.02   $54.00   $54.00  
  Purchase #7 $186.49   3.423%   $192.8736   $192.87   $192.85   $192.90  
  7 purchase totals = $865.35       $947.5020   $947.50   $947.45   $947.50