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 $84.67   12.170%   $94.9743   $94.97   $94.95   $95.00  
  Purchase #2 $201.34   8.241%   $217.9324   $217.93   $217.95   $217.90  
  Purchase #3 $21.97   3.390%   $22.7148   $22.71   $22.70   $22.70  
  Purchase #4 $218.99   5.287%   $230.568   $230.57   $230.55   $230.60  
  Purchase #5 $155.39   11.396%   $173.0982   $173.10   $173.10   $173.10  
  Purchase #6 $173.54   4.663%   $181.6322   $181.63   $181.65   $181.60  
  Purchase #7 $146.28   8.415%   $158.5895   $158.59   $158.60   $158.60  
  7 purchase totals = $1,002.18       $1,079.5094   $1,079.50   $1,079.50   $1,079.50