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	$61.56	3.523%	$63.7288	$63.73	$63.75	$63.70
Purchase #2	$94.30	12.269%	$105.8697	$105.87	$105.85	$105.90
Purchase #3	$94.58	6.722%	$100.9377	$100.94	$100.95	$100.90
Purchase #4	$16.67	7.417%	$17.9064	$17.91	$17.90	$17.90
Purchase #5	$22.27	5.539%	$23.5035	$23.50	$23.50	$23.50
Purchase #6	$249.64	5.710%	$263.8944	$263.89	$263.90	$263.90
Purchase #7	$43.74	4.535%	$45.7236	$45.72	$45.70	$45.70
7 purchase totals =	$582.76		$621.5641	$621.56	$621.55	$621.50