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	$85.46	5.417%	$90.0894	$90.09	$90.10	$90.10
Purchase #2	$96.46	5.306%	$101.5782	$101.58	$101.60	$101.60
Purchase #3	$160.35	13.677%	$182.2811	$182.28	$182.30	$182.30
Purchase #4	$144.47	7.766%	$155.6895	$155.69	$155.70	$155.70
Purchase #5	$223.59	5.370%	$235.5968	$235.60	$235.60	$235.60
Purchase #6	$141.67	10.308%	$156.2733	$156.27	$156.25	$156.30
Purchase #7	$58.88	5.616%	$62.1867	$62.19	$62.20	$62.20
7 purchase totals =	$910.88		$983.6950	$983.70	$983.75	$983.80