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	$56.52	9.274%	$61.7617	$61.76	$61.75	$61.80
Purchase #2	$214.27	4.276%	$223.4322	$223.43	$223.45	$223.40
Purchase #3	$161.30	6.433%	$171.6764	$171.68	$171.70	$171.70
Purchase #4	$188.66	5.331%	$198.7175	$198.72	$198.70	$198.70
Purchase #5	$170.72	11.573%	$190.4774	$190.48	$190.50	$190.50
Purchase #6	$151.58	9.255%	$165.6087	$165.61	$165.60	$165.60
Purchase #7	$165.80	6.282%	$176.2156	$176.22	$176.20	$176.20
7 purchase totals =	$1,108.85		$1,187.8895	$1,187.90	$1,187.90	$1,187.90