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	$193.91	3.268%	$200.247	$200.25	$200.25	$200.20
Purchase #2	$193.64	8.105%	$209.3345	$209.33	$209.35	$209.30
Purchase #3	$59.41	5.343%	$62.5843	$62.58	$62.60	$62.60
Purchase #4	$144.79	11.784%	$161.8521	$161.85	$161.85	$161.90
Purchase #5	$48.59	6.224%	$51.6142	$51.61	$51.60	$51.60
Purchase #6	$222.90	9.479%	$244.0287	$244.03	$244.05	$244.00
Purchase #7	$101.81	10.611%	$112.6131	$112.61	$112.60	$112.60
7 purchase totals =	$965.05		$1,042.2739	$1,042.26	$1,042.30	$1,042.20