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	$111.55	11.136%	$123.9722	$123.97	$123.95	$124.00
Purchase #2	$135.89	11.159%	$151.054	$151.05	$151.05	$151.10
Purchase #3	$45.45	5.706%	$48.0434	$48.04	$48.05	$48.00
Purchase #4	$148.28	13.739%	$168.6522	$168.65	$168.65	$168.70
Purchase #5	$247.50	7.187%	$265.2878	$265.29	$265.30	$265.30
Purchase #6	$149.60	13.829%	$170.2882	$170.29	$170.30	$170.30
Purchase #7	$237.33	6.718%	$253.2738	$253.27	$253.25	$253.30
7 purchase totals =	$1,075.60		$1,180.5716	$1,180.56	$1,180.55	$1,180.70