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	$58.59	5.124%	$61.5922	$61.59	$61.60	$61.60
Purchase #2	$119.58	3.470%	$123.7294	$123.73	$123.75	$123.70
Purchase #3	$128.77	11.172%	$143.1562	$143.16	$143.15	$143.20
Purchase #4	$213.40	6.214%	$226.6607	$226.66	$226.65	$226.70
Purchase #5	$232.37	8.178%	$251.3732	$251.37	$251.35	$251.40
Purchase #6	$105.40	7.511%	$113.3166	$113.32	$113.30	$113.30
Purchase #7	$210.41	13.543%	$238.9058	$238.91	$238.90	$238.90
7 purchase totals =	$1,068.52		$1,158.7341	$1,158.74	$1,158.70	$1,158.80