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 $183.62   11.745%   $205.1862   $205.19   $205.20   $205.20  
  Purchase #2 $84.60   9.517%   $92.6514   $92.65   $92.65   $92.70  
  Purchase #3 $32.54   10.523%   $35.9642   $35.96   $35.95   $36.00  
  Purchase #4 $48.68   6.325%   $51.759   $51.76   $51.75   $51.80  
  Purchase #5 $189.53   3.213%   $195.6196   $195.62   $195.60   $195.60  
  Purchase #6 $31.32   10.250%   $34.5303   $34.53   $34.55   $34.50  
  Purchase #7 $232.65   11.569%   $259.5653   $259.57   $259.55   $259.60  
  7 purchase totals = $802.94       $875.2760   $875.28   $875.25   $875.40