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 $54.58   13.567%   $61.9849   $61.98   $62.00   $62.00  
  Purchase #2 $150.78   12.282%   $169.2988   $169.30   $169.30   $169.30  
  Purchase #3 $80.52   9.118%   $87.8618   $87.86   $87.85   $87.90  
  Purchase #4 $232.58   9.492%   $254.6565   $254.66   $254.65   $254.70  
  Purchase #5 $160.30   5.370%   $168.9081   $168.91   $168.90   $168.90  
  Purchase #6 $54.99   7.585%   $59.161   $59.16   $59.15   $59.20  
  Purchase #7 $164.56   12.323%   $184.8387   $184.84   $184.85   $184.80  
  7 purchase totals = $898.31       $986.7098   $986.71   $986.70   $986.80