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 $22.61   11.561%   $25.2239   $25.22   $25.20   $25.20  
  Purchase #2 $201.89   12.157%   $226.4338   $226.43   $226.45   $226.40  
  Purchase #3 $162.90   4.544%   $170.3022   $170.30   $170.30   $170.30  
  Purchase #4 $68.58   9.624%   $75.1801   $75.18   $75.20   $75.20  
  Purchase #5 $37.41   4.114%   $38.949   $38.95   $38.95   $38.90  
  Purchase #6 $190.83   7.431%   $205.0106   $205.01   $205.00   $205.00  
  Purchase #7 $17.65   13.353%   $20.0068   $20.01   $20.00   $20.00  
  7 purchase totals = $701.87       $761.1064   $761.10   $761.10   $761.00