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	$60.50	3.121%	$62.3882	$62.39	$62.40	$62.40
Purchase #2	$105.31	3.816%	$109.3286	$109.33	$109.35	$109.30
Purchase #3	$47.36	13.268%	$53.6437	$53.64	$53.65	$53.60
Purchase #4	$18.28	3.512%	$18.922	$18.92	$18.90	$18.90
Purchase #5	$178.92	3.821%	$185.7565	$185.76	$185.75	$185.80
Purchase #6	$195.40	9.603%	$214.1643	$214.16	$214.15	$214.20
Purchase #7	$204.73	11.313%	$227.8911	$227.89	$227.90	$227.90
7 purchase totals =	$810.50		$872.0944	$872.09	$872.10	$872.10