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	$197.97	6.442%	$210.7232	$210.72	$210.70	$210.70
Purchase #2	$97.69	13.648%	$111.0227	$111.02	$111.00	$111.00
Purchase #3	$244.47	6.668%	$260.7713	$260.77	$260.75	$260.80
Purchase #4	$160.55	3.602%	$166.333	$166.33	$166.35	$166.30
Purchase #5	$189.37	13.217%	$214.399	$214.40	$214.40	$214.40
Purchase #6	$228.77	4.243%	$238.4767	$238.48	$238.50	$238.50
Purchase #7	$160.40	4.369%	$167.4079	$167.41	$167.40	$167.40
7 purchase totals =	$1,279.22		$1,369.1338	$1,369.13	$1,369.10	$1,369.10