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	$162.71	6.353%	$173.047	$173.05	$173.05	$173.00
Purchase #2	$82.25	11.107%	$91.3855	$91.39	$91.40	$91.40
Purchase #3	$121.98	4.505%	$127.4752	$127.48	$127.50	$127.50
Purchase #4	$199.72	4.206%	$208.1202	$208.12	$208.10	$208.10
Purchase #5	$141.76	5.268%	$149.2279	$149.23	$149.25	$149.20
Purchase #6	$50.68	10.396%	$55.9487	$55.95	$55.95	$55.90
Purchase #7	$16.45	12.175%	$18.4528	$18.45	$18.45	$18.50
7 purchase totals =	$775.55		$823.6573	$823.67	$823.70	$823.60