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 $194.81   5.532%   $205.5869   $205.59   $205.60   $205.60  
  Purchase #2 $131.66   3.549%   $136.3326   $136.33   $136.35   $136.30  
  Purchase #3 $43.94   13.828%   $50.016   $50.02   $50.00   $50.00  
  Purchase #4 $200.68   3.569%   $207.8423   $207.84   $207.85   $207.80  
  Purchase #5 $111.70   12.737%   $125.9272   $125.93   $125.95   $125.90  
  Purchase #6 $106.86   3.415%   $110.5093   $110.51   $110.50   $110.50  
  Purchase #7 $61.83   6.144%   $65.6288   $65.63   $65.65   $65.60  
  7 purchase totals = $851.48       $901.8431   $901.85   $901.90   $901.70