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	$39.25	8.629%	$42.6369	$42.64	$42.65	$42.60
Purchase #2	$54.32	6.354%	$57.7715	$57.77	$57.75	$57.80
Purchase #3	$10.85	3.573%	$11.2377	$11.24	$11.25	$11.20
Purchase #4	$171.60	5.165%	$180.4631	$180.46	$180.45	$180.50
Purchase #5	$229.90	13.481%	$260.8928	$260.89	$260.90	$260.90
Purchase #6	$34.84	7.560%	$37.4739	$37.47	$37.45	$37.50
Purchase #7	$163.51	5.705%	$172.8382	$172.84	$172.85	$172.80
7 purchase totals =	$704.27		$763.3141	$763.31	$763.30	$763.30