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 $44.82   6.191%   $47.5948   $47.59   $47.60   $47.60  
  Purchase #2 $199.63   3.247%   $206.112   $206.11   $206.10   $206.10  
  Purchase #3 $155.39   8.240%   $168.1941   $168.19   $168.20   $168.20  
  Purchase #4 $142.54   8.251%   $154.301   $154.30   $154.30   $154.30  
  Purchase #5 $201.72   9.717%   $221.3211   $221.32   $221.30   $221.30  
  Purchase #6 $68.77   3.727%   $71.3331   $71.33   $71.35   $71.30  
  Purchase #7 $202.73   11.810%   $226.6724   $226.67   $226.65   $226.70  
  7 purchase totals = $1,015.60       $1,095.5285   $1,095.51   $1,095.50   $1,095.50