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 $55.97   10.722%   $61.9711   $61.97   $61.95   $62.00  
  Purchase #2 $107.58   10.304%   $118.665   $118.67   $118.65   $118.70  
  Purchase #3 $193.71   9.663%   $212.4282   $212.43   $212.45   $212.40  
  Purchase #4 $94.86   3.441%   $98.1241   $98.12   $98.10   $98.10  
  Purchase #5 $104.96   3.486%   $108.6189   $108.62   $108.60   $108.60  
  Purchase #6 $64.67   3.385%   $66.8591   $66.86   $66.85   $66.90  
  Purchase #7 $198.97   7.712%   $214.3146   $214.31   $214.30   $214.30  
  7 purchase totals = $820.72       $880.9810   $880.98   $880.90   $881.00