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 $216.58   3.195%   $223.4997   $223.50   $223.50   $223.50  
  Purchase #2 $226.90   6.128%   $240.8044   $240.80   $240.80   $240.80  
  Purchase #3 $209.42   11.433%   $233.363   $233.36   $233.35   $233.40  
  Purchase #4 $24.27   5.677%   $25.6478   $25.65   $25.65   $25.60  
  Purchase #5 $52.82   5.780%   $55.873   $55.87   $55.85   $55.90  
  Purchase #6 $222.45   4.237%   $231.8752   $231.88   $231.90   $231.90  
  Purchase #7 $108.64   6.593%   $115.8026   $115.80   $115.80   $115.80  
  7 purchase totals = $1,061.08       $1,126.8657   $1,126.86   $1,126.85   $1,126.90