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 $87.46   8.397%   $94.804   $94.80   $94.80   $94.80  
  Purchase #2 $180.82   10.215%   $199.2908   $199.29   $199.30   $199.30  
  Purchase #3 $230.54   7.612%   $248.0887   $248.09   $248.10   $248.10  
  Purchase #4 $144.54   6.658%   $154.1635   $154.16   $154.15   $154.20  
  Purchase #5 $189.47   8.120%   $204.855   $204.86   $204.85   $204.90  
  Purchase #6 $169.29   3.769%   $175.6705   $175.67   $175.65   $175.70  
  Purchase #7 $238.71   3.239%   $246.4418   $246.44   $246.45   $246.40  
  7 purchase totals = $1,240.83       $1,323.3143   $1,323.31   $1,323.30   $1,323.40