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 $195.96   5.236%   $206.2205   $206.22   $206.20   $206.20  
  Purchase #2 $43.55   9.571%   $47.7182   $47.72   $47.70   $47.70  
  Purchase #3 $170.25   11.589%   $189.9803   $189.98   $190.00   $190.00  
  Purchase #4 $109.78   13.819%   $124.9505   $124.95   $124.95   $125.00  
  Purchase #5 $90.28   4.750%   $94.5683   $94.57   $94.55   $94.60  
  Purchase #6 $213.99   5.715%   $226.2195   $226.22   $226.20   $226.20  
  Purchase #7 $220.60   9.282%   $241.0761   $241.08   $241.10   $241.10  
  7 purchase totals = $1,044.41       $1,130.7334   $1,130.74   $1,130.70   $1,130.80