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 $69.48   5.790%   $73.5029   $73.50   $73.50   $73.50  
  Purchase #2 $217.84   11.301%   $242.4581   $242.46   $242.45   $242.50  
  Purchase #3 $244.85   12.406%   $275.2261   $275.23   $275.25   $275.20  
  Purchase #4 $160.68   12.675%   $181.0462   $181.05   $181.05   $181.00  
  Purchase #5 $168.55   10.664%   $186.5242   $186.52   $186.50   $186.50  
  Purchase #6 $6.55   9.455%   $7.1693   $7.17   $7.15   $7.20  
  Purchase #7 $199.97   5.245%   $210.4584   $210.46   $210.45   $210.50  
  7 purchase totals = $1,067.92       $1,176.3852   $1,176.39   $1,176.35   $1,176.40