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 $62.93   9.559%   $68.9455   $68.95   $68.95   $68.90  
  Purchase #2 $170.95   11.130%   $189.9767   $189.98   $190.00   $190.00  
  Purchase #3 $159.44   13.671%   $181.237   $181.24   $181.25   $181.20  
  Purchase #4 $214.70   7.617%   $231.0537   $231.05   $231.05   $231.10  
  Purchase #5 $225.39   6.650%   $240.3784   $240.38   $240.40   $240.40  
  Purchase #6 $108.86   5.503%   $114.8506   $114.85   $114.85   $114.90  
  Purchase #7 $142.69   4.792%   $149.5277   $149.53   $149.55   $149.50  
  7 purchase totals = $1,084.96       $1,175.9696   $1,175.98   $1,176.05   $1,176.00