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 $195.76   9.751%   $214.8486   $214.85   $214.85   $214.80  
  Purchase #2 $47.97   4.365%   $50.0639   $50.06   $50.05   $50.10  
  Purchase #3 $199.92   4.842%   $209.6001   $209.60   $209.60   $209.60  
  Purchase #4 $40.59   5.867%   $42.9714   $42.97   $42.95   $43.00  
  Purchase #5 $103.41   5.300%   $108.8907   $108.89   $108.90   $108.90  
  Purchase #6 $197.33   3.667%   $204.5661   $204.57   $204.55   $204.60  
  Purchase #7 $49.33   3.194%   $50.9056   $50.91   $50.90   $50.90  
  7 purchase totals = $834.31       $881.8464   $881.85   $881.80   $881.90