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	$184.82	6.465%	$196.7686	$196.77	$196.75	$196.80
Purchase #2	$221.47	5.494%	$233.6376	$233.64	$233.65	$233.60
Purchase #3	$217.80	12.489%	$245.001	$245.00	$245.00	$245.00
Purchase #4	$66.45	4.640%	$69.5333	$69.53	$69.55	$69.50
Purchase #5	$154.66	10.763%	$171.3061	$171.31	$171.30	$171.30
Purchase #6	$51.54	10.128%	$56.76	$56.76	$56.75	$56.80
Purchase #7	$224.54	6.251%	$238.576	$238.58	$238.60	$238.60
7 purchase totals =	$1,121.28		$1,211.5826	$1,211.59	$1,211.60	$1,211.60