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	$153.41	9.342%	$167.7416	$167.74	$167.75	$167.70
Purchase #2	$191.26	13.613%	$217.2962	$217.30	$217.30	$217.30
Purchase #3	$240.86	9.114%	$262.812	$262.81	$262.80	$262.80
Purchase #4	$6.85	6.822%	$7.3173	$7.32	$7.30	$7.30
Purchase #5	$170.89	8.261%	$185.0072	$185.01	$185.00	$185.00
Purchase #6	$136.88	12.627%	$154.1638	$154.16	$154.15	$154.20
Purchase #7	$149.73	10.407%	$165.3124	$165.31	$165.30	$165.30
7 purchase totals =	$1,049.88		$1,159.6505	$1,159.65	$1,159.60	$1,159.60