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	$194.29	8.263%	$210.3442	$210.34	$210.35	$210.30
Purchase #2	$153.34	5.136%	$161.2155	$161.22	$161.20	$161.20
Purchase #3	$174.35	6.475%	$185.6392	$185.64	$185.65	$185.60
Purchase #4	$137.29	10.323%	$151.4624	$151.46	$151.45	$151.50
Purchase #5	$130.63	10.265%	$144.0392	$144.04	$144.05	$144.00
Purchase #6	$47.43	9.461%	$51.9174	$51.92	$51.90	$51.90
Purchase #7	$179.61	13.663%	$204.1501	$204.15	$204.15	$204.20
7 purchase totals =	$1,016.94		$1,108.7680	$1,108.77	$1,108.75	$1,108.70