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 $86.84   9.593%   $95.1706   $95.17   $95.15   $95.20  
  Purchase #2 $201.57   13.672%   $229.1287   $229.13   $229.15   $229.10  
  Purchase #3 $219.58   12.707%   $247.482   $247.48   $247.50   $247.50  
  Purchase #4 $42.53   9.325%   $46.4959   $46.50   $46.50   $46.50  
  Purchase #5 $52.94   11.862%   $59.2197   $59.22   $59.20   $59.20  
  Purchase #6 $170.61   12.632%   $192.1615   $192.16   $192.15   $192.20  
  Purchase #7 $191.66   11.648%   $213.9846   $213.98   $214.00   $214.00  
  7 purchase totals = $965.73       $1,083.6430   $1,083.64   $1,083.65   $1,083.70