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	$33.43	3.123%	$34.474	$34.47	$34.45	$34.50
Purchase #2	$127.82	11.535%	$142.564	$142.56	$142.55	$142.60
Purchase #3	$153.74	11.633%	$171.6246	$171.62	$171.60	$171.60
Purchase #4	$101.90	5.506%	$107.5106	$107.51	$107.50	$107.50
Purchase #5	$49.53	5.551%	$52.2794	$52.28	$52.30	$52.30
Purchase #6	$170.82	10.138%	$188.1377	$188.14	$188.15	$188.10
Purchase #7	$180.52	4.327%	$188.3311	$188.33	$188.35	$188.30
7 purchase totals =	$817.76		$884.9214	$884.91	$884.90	$884.90