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 $61.44   10.761%   $68.0516   $68.05   $68.05   $68.10  
  Purchase #2 $101.56   6.295%   $107.9532   $107.95   $107.95   $108.00  
  Purchase #3 $185.43   9.194%   $202.4784   $202.48   $202.50   $202.50  
  Purchase #4 $200.71   5.817%   $212.3853   $212.39   $212.40   $212.40  
  Purchase #5 $245.86   8.444%   $266.6204   $266.62   $266.60   $266.60  
  Purchase #6 $215.82   8.735%   $234.6719   $234.67   $234.65   $234.70  
  Purchase #7 $137.75   11.562%   $153.6767   $153.68   $153.70   $153.70  
  7 purchase totals = $1,148.57       $1,245.8375   $1,245.84   $1,245.85   $1,246.00