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	$89.47	7.178%	$95.8922	$95.89	$95.90	$95.90
Purchase #2	$241.77	4.700%	$253.1332	$253.13	$253.15	$253.10
Purchase #3	$9.90	10.736%	$10.9629	$10.96	$10.95	$11.00
Purchase #4	$155.99	10.535%	$172.4235	$172.42	$172.40	$172.40
Purchase #5	$238.37	10.510%	$263.4227	$263.42	$263.40	$263.40
Purchase #6	$46.51	4.115%	$48.4239	$48.42	$48.40	$48.40
Purchase #7	$229.48	13.160%	$259.6796	$259.68	$259.70	$259.70
7 purchase totals =	$1,011.49		$1,103.9380	$1,103.92	$1,103.90	$1,103.90