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	$161.84	7.347%	$173.7304	$173.73	$173.75	$173.70
Purchase #2	$7.40	8.240%	$8.0098	$8.01	$8.00	$8.00
Purchase #3	$110.55	11.558%	$123.3274	$123.33	$123.35	$123.30
Purchase #4	$39.87	11.566%	$44.4814	$44.48	$44.50	$44.50
Purchase #5	$233.74	9.168%	$255.1693	$255.17	$255.15	$255.20
Purchase #6	$248.89	10.550%	$275.1479	$275.15	$275.15	$275.10
Purchase #7	$226.56	13.368%	$256.8465	$256.85	$256.85	$256.80
7 purchase totals =	$1,028.85		$1,136.7127	$1,136.72	$1,136.75	$1,136.60