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 $240.41   11.292%   $267.5571   $267.56   $267.55   $267.60  
  Purchase #2 $85.96   8.447%   $93.221   $93.22   $93.20   $93.20  
  Purchase #3 $168.97   13.818%   $192.3183   $192.32   $192.30   $192.30  
  Purchase #4 $169.64   10.297%   $187.1078   $187.11   $187.10   $187.10  
  Purchase #5 $168.79   10.313%   $186.1973   $186.20   $186.20   $186.20  
  Purchase #6 $151.28   10.553%   $167.2446   $167.24   $167.25   $167.20  
  Purchase #7 $22.97   6.707%   $24.5106   $24.51   $24.50   $24.50  
  7 purchase totals = $1,008.02       $1,118.1567   $1,118.16   $1,118.10   $1,118.10