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	$211.31	8.321%	$228.8931	$228.89	$228.90	$228.90
Purchase #2	$128.71	13.192%	$145.6894	$145.69	$145.70	$145.70
Purchase #3	$48.37	5.141%	$50.8567	$50.86	$50.85	$50.90
Purchase #4	$191.53	6.747%	$204.4525	$204.45	$204.45	$204.50
Purchase #5	$161.68	6.488%	$172.1698	$172.17	$172.15	$172.20
Purchase #6	$83.88	12.296%	$94.1939	$94.19	$94.20	$94.20
Purchase #7	$98.37	7.574%	$105.8205	$105.82	$105.80	$105.80
7 purchase totals =	$923.85		$1,002.0759	$1,002.07	$1,002.05	$1,002.20