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 $31.71   13.350%   $35.9433   $35.94   $35.95   $35.90  
  Purchase #2 $172.26   13.199%   $194.9966   $195.00   $195.00   $195.00  
  Purchase #3 $225.44   11.279%   $250.8674   $250.87   $250.85   $250.90  
  Purchase #4 $20.80   3.643%   $21.5577   $21.56   $21.55   $21.60  
  Purchase #5 $182.82   13.378%   $207.2777   $207.28   $207.30   $207.30  
  Purchase #6 $147.60   9.857%   $162.1489   $162.15   $162.15   $162.10  
  Purchase #7 $212.36   13.777%   $241.6168   $241.62   $241.60   $241.60  
  7 purchase totals = $992.99       $1,114.4084   $1,114.42   $1,114.40   $1,114.40