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	$96.34	9.673%	$105.659	$105.66	$105.65	$105.70
Purchase #2	$202.78	13.734%	$230.6298	$230.63	$230.65	$230.60
Purchase #3	$239.35	9.169%	$261.296	$261.30	$261.30	$261.30
Purchase #4	$98.65	13.167%	$111.6392	$111.64	$111.65	$111.60
Purchase #5	$138.31	3.501%	$143.1522	$143.15	$143.15	$143.20
Purchase #6	$20.43	5.234%	$21.4993	$21.50	$21.50	$21.50
Purchase #7	$216.28	6.776%	$230.9351	$230.94	$230.95	$230.90
7 purchase totals =	$1,012.14		$1,104.8106	$1,104.82	$1,104.85	$1,104.80