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	$163.38	12.798%	$184.2894	$184.29	$184.30	$184.30
Purchase #2	$22.83	4.780%	$23.9213	$23.92	$23.90	$23.90
Purchase #3	$211.50	4.792%	$221.6351	$221.64	$221.65	$221.60
Purchase #4	$200.81	12.501%	$225.9133	$225.91	$225.90	$225.90
Purchase #5	$96.66	8.807%	$105.1728	$105.17	$105.15	$105.20
Purchase #6	$63.57	11.664%	$70.9848	$70.98	$71.00	$71.00
Purchase #7	$243.95	4.782%	$255.6157	$255.62	$255.60	$255.60
7 purchase totals =	$1,002.70		$1,087.5324	$1,087.53	$1,087.50	$1,087.50