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 $65.84   5.267%   $69.3078   $69.31   $69.30   $69.30  
  Purchase #2 $242.61   12.390%   $272.6694   $272.67   $272.65   $272.70  
  Purchase #3 $242.66   9.674%   $266.1349   $266.13   $266.15   $266.10  
  Purchase #4 $60.34   10.325%   $66.5701   $66.57   $66.55   $66.60  
  Purchase #5 $75.99   4.414%   $79.3442   $79.34   $79.35   $79.30  
  Purchase #6 $233.52   10.182%   $257.297   $257.30   $257.30   $257.30  
  Purchase #7 $100.36   6.269%   $106.6516   $106.65   $106.65   $106.70  
  7 purchase totals = $1,021.32       $1,117.9750   $1,117.97   $1,117.95   $1,118.00