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 $85.31   13.465%   $96.797   $96.80   $96.80   $96.80  
  Purchase #2 $146.70   7.274%   $157.371   $157.37   $157.35   $157.40  
  Purchase #3 $223.65   8.357%   $242.3404   $242.34   $242.35   $242.30  
  Purchase #4 $178.95   8.762%   $194.6296   $194.63   $194.65   $194.60  
  Purchase #5 $190.50   5.493%   $200.9642   $200.96   $200.95   $201.00  
  Purchase #6 $179.85   13.742%   $204.565   $204.57   $204.55   $204.60  
  Purchase #7 $112.93   8.198%   $122.188   $122.19   $122.20   $122.20  
  7 purchase totals = $1,117.89       $1,218.8552   $1,218.86   $1,218.85   $1,218.90