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 $184.64   11.554%   $205.9733   $205.97   $205.95   $206.00  
  Purchase #2 $42.80   4.715%   $44.818   $44.82   $44.80   $44.80  
  Purchase #3 $116.34   6.746%   $124.1883   $124.19   $124.20   $124.20  
  Purchase #4 $98.86   10.730%   $109.4677   $109.47   $109.45   $109.50  
  Purchase #5 $168.86   5.773%   $178.6083   $178.61   $178.60   $178.60  
  Purchase #6 $161.35   5.151%   $169.6611   $169.66   $169.65   $169.70  
  Purchase #7 $207.92   3.504%   $215.2055   $215.21   $215.20   $215.20  
  7 purchase totals = $980.77       $1,047.9222   $1,047.93   $1,047.85   $1,048.00