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	$41.63	4.182%	$43.371	$43.37	$43.35	$43.40
Purchase #2	$72.91	12.161%	$81.7766	$81.78	$81.80	$81.80
Purchase #3	$40.36	10.161%	$44.461	$44.46	$44.45	$44.50
Purchase #4	$91.72	11.553%	$102.3164	$102.32	$102.30	$102.30
Purchase #5	$49.51	12.154%	$55.5274	$55.53	$55.55	$55.50
Purchase #6	$96.63	4.315%	$100.7996	$100.80	$100.80	$100.80
Purchase #7	$45.42	11.439%	$50.6156	$50.62	$50.60	$50.60
7 purchase totals =	$438.18		$478.8676	$478.88	$478.85	$478.90