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	$96.25	9.423%	$105.3196	$105.32	$105.30	$105.30
Purchase #2	$62.72	8.164%	$67.8405	$67.84	$67.85	$67.80
Purchase #3	$68.36	13.693%	$77.7205	$77.72	$77.70	$77.70
Purchase #4	$47.34	6.134%	$50.2438	$50.24	$50.25	$50.20
Purchase #5	$6.85	4.272%	$7.1426	$7.14	$7.15	$7.10
Purchase #6	$39.50	3.333%	$40.8165	$40.82	$40.80	$40.80
Purchase #7	$85.88	11.316%	$95.5982	$95.60	$95.60	$95.60
7 purchase totals =	$406.90		$444.6817	$444.68	$444.65	$444.50