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 $115.88   8.165%   $125.3416   $125.34   $125.35   $125.30  
  Purchase #2 $218.95   9.296%   $239.3036   $239.30   $239.30   $239.30  
  Purchase #3 $225.82   5.787%   $238.8882   $238.89   $238.90   $238.90  
  Purchase #4 $186.50   8.129%   $201.6606   $201.66   $201.65   $201.70  
  Purchase #5 $246.60   9.203%   $269.2946   $269.29   $269.30   $269.30  
  Purchase #6 $242.33   12.212%   $271.9233   $271.92   $271.90   $271.90  
  Purchase #7 $128.50   5.567%   $135.6536   $135.65   $135.65   $135.70  
  7 purchase totals = $1,364.58       $1,482.0655   $1,482.05   $1,482.05   $1,482.10