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	$55.89	8.636%	$60.7167	$60.72	$60.70	$60.70
Purchase #2	$69.43	5.522%	$73.2639	$73.26	$73.25	$73.30
Purchase #3	$205.43	8.624%	$223.1463	$223.15	$223.15	$223.10
Purchase #4	$141.81	8.228%	$153.4781	$153.48	$153.50	$153.50
Purchase #5	$224.89	12.843%	$253.7726	$253.77	$253.75	$253.80
Purchase #6	$91.77	13.211%	$103.8937	$103.89	$103.90	$103.90
Purchase #7	$5.90	4.429%	$6.1613	$6.16	$6.15	$6.20
7 purchase totals =	$795.12		$874.4326	$874.43	$874.40	$874.50