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	$69.87	6.610%	$74.4884	$74.49	$74.50	$74.50
Purchase #2	$51.59	12.274%	$57.9222	$57.92	$57.90	$57.90
Purchase #3	$162.97	5.640%	$172.1615	$172.16	$172.15	$172.20
Purchase #4	$59.80	12.664%	$67.3731	$67.37	$67.35	$67.40
Purchase #5	$243.65	5.187%	$256.2881	$256.29	$256.30	$256.30
Purchase #6	$10.33	13.642%	$11.7392	$11.74	$11.75	$11.70
Purchase #7	$173.79	6.617%	$185.2897	$185.29	$185.30	$185.30
7 purchase totals =	$772.00		$825.2622	$825.26	$825.25	$825.30