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 $12.85   10.501%   $14.1994   $14.20   $14.20   $14.20  
  Purchase #2 $246.95   11.403%   $275.1097   $275.11   $275.10   $275.10  
  Purchase #3 $53.53   3.649%   $55.4833   $55.48   $55.50   $55.50  
  Purchase #4 $184.89   5.348%   $194.7779   $194.78   $194.80   $194.80  
  Purchase #5 $70.50   3.702%   $73.1099   $73.11   $73.10   $73.10  
  Purchase #6 $214.46   10.210%   $236.3564   $236.36   $236.35   $236.40  
  Purchase #7 $223.94   8.756%   $243.5482   $243.55   $243.55   $243.50  
  7 purchase totals = $1,007.12       $1,092.5848   $1,092.59   $1,092.60   $1,092.60