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	$68.69	13.361%	$77.8677	$77.87	$77.85	$77.90
Purchase #2	$150.41	3.619%	$155.8533	$155.85	$155.85	$155.90
Purchase #3	$146.49	4.644%	$153.293	$153.29	$153.30	$153.30
Purchase #4	$224.92	5.525%	$237.3468	$237.35	$237.35	$237.30
Purchase #5	$172.32	6.506%	$183.5311	$183.53	$183.55	$183.50
Purchase #6	$211.55	5.306%	$222.7748	$222.77	$222.75	$222.80
Purchase #7	$45.74	11.247%	$50.8844	$50.88	$50.90	$50.90
7 purchase totals =	$1,020.12		$1,081.5511	$1,081.54	$1,081.55	$1,081.60