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	$155.74	11.377%	$173.4585	$173.46	$173.45	$173.50
Purchase #2	$16.95	7.122%	$18.1572	$18.16	$18.15	$18.20
Purchase #3	$155.79	4.255%	$162.4189	$162.42	$162.40	$162.40
Purchase #4	$126.64	12.381%	$142.3193	$142.32	$142.30	$142.30
Purchase #5	$248.48	4.284%	$259.1249	$259.12	$259.10	$259.10
Purchase #6	$111.66	10.518%	$123.4044	$123.40	$123.40	$123.40
Purchase #7	$134.87	7.796%	$145.3845	$145.38	$145.40	$145.40
7 purchase totals =	$950.13		$1,024.2677	$1,024.26	$1,024.20	$1,024.30