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 $118.61   3.669%   $122.9618   $122.96   $122.95   $123.00  
  Purchase #2 $162.35   12.664%   $182.91   $182.91   $182.90   $182.90  
  Purchase #3 $61.42   8.486%   $66.6321   $66.63   $66.65   $66.60  
  Purchase #4 $235.47   13.612%   $267.5222   $267.52   $267.50   $267.50  
  Purchase #5 $149.76   3.174%   $154.5134   $154.51   $154.50   $154.50  
  Purchase #6 $220.60   6.609%   $235.1795   $235.18   $235.20   $235.20  
  Purchase #7 $86.94   7.746%   $93.6744   $93.67   $93.65   $93.70  
  7 purchase totals = $1,035.15       $1,123.3934   $1,123.38   $1,123.35   $1,123.40