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 $176.41   11.420%   $196.556   $196.56   $196.55   $196.60  
  Purchase #2 $47.55   8.584%   $51.6317   $51.63   $51.65   $51.60  
  Purchase #3 $50.76   6.428%   $54.0229   $54.02   $54.00   $54.00  
  Purchase #4 $156.84   10.108%   $172.6934   $172.69   $172.70   $172.70  
  Purchase #5 $117.87   6.643%   $125.7001   $125.70   $125.70   $125.70  
  Purchase #6 $192.62   4.414%   $201.1222   $201.12   $201.10   $201.10  
  Purchase #7 $116.94   10.205%   $128.8737   $128.87   $128.85   $128.90  
  7 purchase totals = $858.99       $930.6000   $930.59   $930.55   $930.60