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	$7.25	6.488%	$7.7204	$7.72	$7.70	$7.70
Purchase #2	$20.25	12.550%	$22.7914	$22.79	$22.80	$22.80
Purchase #3	$43.66	6.190%	$46.3626	$46.36	$46.35	$46.40
Purchase #4	$97.91	11.710%	$109.3753	$109.38	$109.40	$109.40
Purchase #5	$10.80	10.667%	$11.952	$11.95	$11.95	$12.00
Purchase #6	$127.30	13.581%	$144.5886	$144.59	$144.60	$144.60
Purchase #7	$34.26	9.303%	$37.4472	$37.45	$37.45	$37.40
7 purchase totals =	$341.43		$380.2375	$380.24	$380.25	$380.30