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 $85.39   7.749%   $92.0069   $92.01   $92.00   $92.00  
  Purchase #2 $118.40   5.735%   $125.1902   $125.19   $125.20   $125.20  
  Purchase #3 $40.79   12.598%   $45.9287   $45.93   $45.95   $45.90  
  Purchase #4 $107.94   9.812%   $118.5311   $118.53   $118.55   $118.50  
  Purchase #5 $86.42   11.633%   $96.4732   $96.47   $96.45   $96.50  
  Purchase #6 $83.54   9.835%   $91.7562   $91.76   $91.75   $91.80  
  Purchase #7 $184.61   9.727%   $202.567   $202.57   $202.55   $202.60  
  7 purchase totals = $707.09       $772.4533   $772.46   $772.45   $772.50