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	$36.44	4.761%	$38.1749	$38.17	$38.15	$38.20
Purchase #2	$182.58	5.548%	$192.7095	$192.71	$192.70	$192.70
Purchase #3	$42.59	5.783%	$45.053	$45.05	$45.05	$45.10
Purchase #4	$102.77	9.645%	$112.6822	$112.68	$112.70	$112.70
Purchase #5	$13.55	13.847%	$15.4263	$15.43	$15.45	$15.40
Purchase #6	$234.66	9.459%	$256.8565	$256.86	$256.85	$256.90
Purchase #7	$153.59	11.604%	$171.4126	$171.41	$171.40	$171.40
7 purchase totals =	$766.18		$832.3150	$832.31	$832.30	$832.40