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 $42.41   3.413%   $43.8575   $43.86   $43.85   $43.90  
  Purchase #2 $214.63   13.829%   $244.3112   $244.31   $244.30   $244.30  
  Purchase #3 $216.45   13.580%   $245.8439   $245.84   $245.85   $245.80  
  Purchase #4 $27.94   9.651%   $30.6365   $30.64   $30.65   $30.60  
  Purchase #5 $18.40   6.476%   $19.5916   $19.59   $19.60   $19.60  
  Purchase #6 $249.96   10.264%   $275.6159   $275.62   $275.60   $275.60  
  Purchase #7 $32.86   6.282%   $34.9243   $34.92   $34.90   $34.90  
  7 purchase totals = $802.65       $894.7809   $894.78   $894.75   $894.70