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	$60.59	4.717%	$63.448	$63.45	$63.45	$63.40
Purchase #2	$205.45	13.494%	$233.1734	$233.17	$233.15	$233.20
Purchase #3	$121.79	4.433%	$127.189	$127.19	$127.20	$127.20
Purchase #4	$67.89	4.117%	$70.685	$70.69	$70.70	$70.70
Purchase #5	$23.53	12.690%	$26.516	$26.52	$26.50	$26.50
Purchase #6	$77.78	10.456%	$85.9127	$85.91	$85.90	$85.90
Purchase #7	$69.83	3.683%	$72.4018	$72.40	$72.40	$72.40
7 purchase totals =	$626.86		$679.3259	$679.33	$679.30	$679.30