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	$81.41	5.272%	$85.7019	$85.70	$85.70	$85.70
Purchase #2	$26.93	10.657%	$29.7999	$29.80	$29.80	$29.80
Purchase #3	$172.27	3.593%	$178.4597	$178.46	$178.45	$178.50
Purchase #4	$114.42	11.775%	$127.893	$127.89	$127.90	$127.90
Purchase #5	$218.75	6.739%	$233.4916	$233.49	$233.50	$233.50
Purchase #6	$48.25	4.667%	$50.5018	$50.50	$50.50	$50.50
Purchase #7	$93.65	11.784%	$104.6857	$104.69	$104.70	$104.70
7 purchase totals =	$755.68		$810.5336	$810.53	$810.55	$810.60