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	$50.44	8.609%	$54.7824	$54.78	$54.80	$54.80
Purchase #2	$187.92	4.290%	$195.9818	$195.98	$196.00	$196.00
Purchase #3	$138.42	10.443%	$152.8752	$152.88	$152.90	$152.90
Purchase #4	$147.76	7.278%	$158.514	$158.51	$158.50	$158.50
Purchase #5	$173.64	3.635%	$179.9518	$179.95	$179.95	$180.00
Purchase #6	$71.82	5.279%	$75.6114	$75.61	$75.60	$75.60
Purchase #7	$173.73	9.195%	$189.7045	$189.70	$189.70	$189.70
7 purchase totals =	$943.73		$1,007.4211	$1,007.41	$1,007.45	$1,007.50