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	$105.98	5.362%	$111.6626	$111.66	$111.65	$111.70
Purchase #2	$212.80	10.565%	$235.2823	$235.28	$235.30	$235.30
Purchase #3	$116.33	4.145%	$121.1519	$121.15	$121.15	$121.20
Purchase #4	$168.25	12.663%	$189.5555	$189.56	$189.55	$189.60
Purchase #5	$179.37	4.268%	$187.0255	$187.03	$187.05	$187.00
Purchase #6	$67.47	11.626%	$75.3141	$75.31	$75.30	$75.30
Purchase #7	$153.25	12.754%	$172.7955	$172.80	$172.80	$172.80
7 purchase totals =	$1,003.45		$1,092.7874	$1,092.79	$1,092.80	$1,092.90