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	$237.74	10.530%	$262.774	$262.77	$262.75	$262.80
Purchase #2	$16.30	11.337%	$18.1479	$18.15	$18.15	$18.10
Purchase #3	$61.62	7.666%	$66.3438	$66.34	$66.35	$66.30
Purchase #4	$63.25	3.272%	$65.3195	$65.32	$65.30	$65.30
Purchase #5	$117.83	7.378%	$126.5235	$126.52	$126.50	$126.50
Purchase #6	$18.44	12.306%	$20.7092	$20.71	$20.70	$20.70
Purchase #7	$185.46	8.188%	$200.6455	$200.65	$200.65	$200.60
7 purchase totals =	$700.64		$760.4634	$760.46	$760.40	$760.30