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 $187.48   3.610%   $194.248   $194.25   $194.25   $194.20  
  Purchase #2 $68.53   9.189%   $74.8272   $74.83   $74.85   $74.80  
  Purchase #3 $164.65   9.525%   $180.3329   $180.33   $180.35   $180.30  
  Purchase #4 $219.73   6.569%   $234.1641   $234.16   $234.15   $234.20  
  Purchase #5 $228.51   7.487%   $245.6185   $245.62   $245.60   $245.60  
  Purchase #6 $168.68   3.160%   $174.0103   $174.01   $174.00   $174.00  
  Purchase #7 $229.39   12.647%   $258.401   $258.40   $258.40   $258.40  
  7 purchase totals = $1,266.97       $1,361.6020   $1,361.60   $1,361.60   $1,361.50