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 $85.58   11.499%   $95.4208   $95.42   $95.40   $95.40  
  Purchase #2 $102.70   13.573%   $116.6395   $116.64   $116.65   $116.60  
  Purchase #3 $47.30   10.826%   $52.4207   $52.42   $52.40   $52.40  
  Purchase #4 $182.70   6.844%   $195.204   $195.20   $195.20   $195.20  
  Purchase #5 $234.77   4.720%   $245.8511   $245.85   $245.85   $245.90  
  Purchase #6 $73.72   9.389%   $80.6416   $80.64   $80.65   $80.60  
  Purchase #7 $190.52   11.390%   $212.2202   $212.22   $212.20   $212.20  
  7 purchase totals = $917.29       $998.3979   $998.39   $998.35   $998.30