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	$59.40	3.637%	$61.5604	$61.56	$61.55	$61.60
Purchase #2	$157.47	9.332%	$172.1651	$172.17	$172.15	$172.20
Purchase #3	$97.87	6.560%	$104.2903	$104.29	$104.30	$104.30
Purchase #4	$226.43	13.210%	$256.3414	$256.34	$256.35	$256.30
Purchase #5	$43.73	3.148%	$45.1066	$45.11	$45.10	$45.10
Purchase #6	$66.45	12.264%	$74.5994	$74.60	$74.60	$74.60
Purchase #7	$165.92	3.275%	$171.3539	$171.35	$171.35	$171.40
7 purchase totals =	$817.27		$885.4171	$885.42	$885.40	$885.50