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 $94.86   8.183%   $102.6224   $102.62   $102.60   $102.60  
  Purchase #2 $204.62   5.167%   $215.1927   $215.19   $215.20   $215.20  
  Purchase #3 $248.54   10.506%   $274.6516   $274.65   $274.65   $274.70  
  Purchase #4 $186.97   3.785%   $194.0468   $194.05   $194.05   $194.00  
  Purchase #5 $199.77   5.747%   $211.2508   $211.25   $211.25   $211.30  
  Purchase #6 $28.85   12.459%   $32.4444   $32.44   $32.45   $32.40  
  Purchase #7 $199.33   12.399%   $224.0449   $224.04   $224.05   $224.00  
  7 purchase totals = $1,162.94       $1,254.2536   $1,254.24   $1,254.25   $1,254.20