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	$53.96	8.860%	$58.7409	$58.74	$58.75	$58.70
Purchase #2	$220.30	8.301%	$238.5871	$238.59	$238.60	$238.60
Purchase #3	$172.63	8.784%	$187.7938	$187.79	$187.80	$187.80
Purchase #4	$32.83	12.792%	$37.0296	$37.03	$37.05	$37.00
Purchase #5	$101.91	9.716%	$111.8116	$111.81	$111.80	$111.80
Purchase #6	$94.29	9.312%	$103.0703	$103.07	$103.05	$103.10
Purchase #7	$57.34	7.569%	$61.6801	$61.68	$61.70	$61.70
7 purchase totals =	$733.26		$798.7134	$798.71	$798.75	$798.70