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 $204.81   13.768%   $233.0082   $233.01   $233.00   $233.00  
  Purchase #2 $209.71   4.795%   $219.7656   $219.77   $219.75   $219.80  
  Purchase #3 $187.33   3.595%   $194.0645   $194.06   $194.05   $194.10  
  Purchase #4 $216.98   9.667%   $237.9555   $237.96   $237.95   $238.00  
  Purchase #5 $215.88   8.224%   $233.634   $233.63   $233.65   $233.60  
  Purchase #6 $183.67   7.552%   $197.5408   $197.54   $197.55   $197.50  
  Purchase #7 $60.59   12.658%   $68.2595   $68.26   $68.25   $68.30  
  7 purchase totals = $1,278.97       $1,384.2281   $1,384.23   $1,384.20   $1,384.30