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	$75.41	9.829%	$82.822	$82.82	$82.80	$82.80
Purchase #2	$88.37	13.690%	$100.4679	$100.47	$100.45	$100.50
Purchase #3	$57.80	5.679%	$61.0825	$61.08	$61.10	$61.10
Purchase #4	$74.86	11.747%	$83.6538	$83.65	$83.65	$83.70
Purchase #5	$193.77	8.507%	$210.254	$210.25	$210.25	$210.30
Purchase #6	$239.44	11.269%	$266.4225	$266.42	$266.40	$266.40
Purchase #7	$46.90	7.808%	$50.562	$50.56	$50.55	$50.60
7 purchase totals =	$776.55		$855.2647	$855.25	$855.20	$855.40