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 $96.53   10.755%   $106.9118   $106.91   $106.90   $106.90  
  Purchase #2 $151.84   4.583%   $158.7988   $158.80   $158.80   $158.80  
  Purchase #3 $153.86   9.441%   $168.3859   $168.39   $168.40   $168.40  
  Purchase #4 $129.50   3.674%   $134.2578   $134.26   $134.25   $134.30  
  Purchase #5 $104.34   9.632%   $114.39   $114.39   $114.40   $114.40  
  Purchase #6 $239.62   11.666%   $267.5741   $267.57   $267.55   $267.60  
  Purchase #7 $232.98   5.819%   $246.5371   $246.54   $246.55   $246.50  
  7 purchase totals = $1,108.67       $1,196.8555   $1,196.86   $1,196.85   $1,196.90