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	$130.88	13.383%	$148.3957	$148.40	$148.40	$148.40
Purchase #2	$123.61	3.499%	$127.9351	$127.94	$127.95	$127.90
Purchase #3	$140.33	9.147%	$153.166	$153.17	$153.15	$153.20
Purchase #4	$118.38	11.297%	$131.7534	$131.75	$131.75	$131.80
Purchase #5	$175.95	9.664%	$192.9538	$192.95	$192.95	$193.00
Purchase #6	$64.42	12.515%	$72.4822	$72.48	$72.50	$72.50
Purchase #7	$127.28	10.746%	$140.9575	$140.96	$140.95	$141.00
7 purchase totals =	$880.85		$967.6437	$967.65	$967.65	$967.80