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	$20.76	10.373%	$22.9134	$22.91	$22.90	$22.90
Purchase #2	$199.77	11.477%	$222.6976	$222.70	$222.70	$222.70
Purchase #3	$89.96	6.265%	$95.596	$95.60	$95.60	$95.60
Purchase #4	$176.74	4.415%	$184.5431	$184.54	$184.55	$184.50
Purchase #5	$151.88	4.429%	$158.6068	$158.61	$158.60	$158.60
Purchase #6	$155.63	9.395%	$170.2514	$170.25	$170.25	$170.30
Purchase #7	$158.71	10.553%	$175.4587	$175.46	$175.45	$175.50
7 purchase totals =	$953.45		$1,030.0670	$1,030.07	$1,030.05	$1,030.10