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	$159.96	3.451%	$165.4802	$165.48	$165.50	$165.50
Purchase #2	$140.88	12.836%	$158.9634	$158.96	$158.95	$159.00
Purchase #3	$139.79	6.591%	$149.0036	$149.00	$149.00	$149.00
Purchase #4	$70.58	3.158%	$72.8089	$72.81	$72.80	$72.80
Purchase #5	$39.68	13.708%	$45.1193	$45.12	$45.10	$45.10
Purchase #6	$12.89	4.592%	$13.4819	$13.48	$13.50	$13.50
Purchase #7	$71.80	12.253%	$80.5977	$80.60	$80.60	$80.60
7 purchase totals =	$635.58		$685.4550	$685.45	$685.45	$685.50