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 $194.97   7.682%   $209.9476   $209.95   $209.95   $209.90  
  Purchase #2 $144.74   5.460%   $152.6428   $152.64   $152.65   $152.60  
  Purchase #3 $250.78   9.545%   $274.717   $274.72   $274.70   $274.70  
  Purchase #4 $24.64   3.575%   $25.5209   $25.52   $25.50   $25.50  
  Purchase #5 $111.36   5.746%   $117.7587   $117.76   $117.75   $117.80  
  Purchase #6 $232.96   3.330%   $240.7176   $240.72   $240.70   $240.70  
  Purchase #7 $238.27   3.167%   $245.816   $245.82   $245.80   $245.80  
  7 purchase totals = $1,197.72       $1,267.1206   $1,267.13   $1,267.05   $1,267.00