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	$240.71	4.325%	$251.1207	$251.12	$251.10	$251.10
Purchase #2	$116.51	12.154%	$130.6706	$130.67	$130.65	$130.70
Purchase #3	$114.52	3.834%	$118.9107	$118.91	$118.90	$118.90
Purchase #4	$203.82	12.254%	$228.7961	$228.80	$228.80	$228.80
Purchase #5	$91.33	7.370%	$98.061	$98.06	$98.05	$98.10
Purchase #6	$153.29	12.413%	$172.3179	$172.32	$172.30	$172.30
Purchase #7	$96.58	7.501%	$103.8245	$103.82	$103.80	$103.80
7 purchase totals =	$1,016.76		$1,103.7015	$1,103.70	$1,103.60	$1,103.70