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	$154.89	7.126%	$165.9275	$165.93	$165.95	$165.90
Purchase #2	$183.63	7.388%	$197.1966	$197.20	$197.20	$197.20
Purchase #3	$222.73	13.264%	$252.2729	$252.27	$252.25	$252.30
Purchase #4	$78.66	13.871%	$89.5709	$89.57	$89.55	$89.60
Purchase #5	$197.93	4.314%	$206.4687	$206.47	$206.45	$206.50
Purchase #6	$31.43	13.829%	$35.7765	$35.78	$35.80	$35.80
Purchase #7	$235.32	12.253%	$264.1538	$264.15	$264.15	$264.20
7 purchase totals =	$1,104.59		$1,211.3669	$1,211.37	$1,211.35	$1,211.50