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	$88.26	11.212%	$98.1557	$98.16	$98.15	$98.20
Purchase #2	$80.71	13.547%	$91.6438	$91.64	$91.65	$91.60
Purchase #3	$95.66	4.698%	$100.1541	$100.15	$100.15	$100.20
Purchase #4	$45.41	10.345%	$50.1077	$50.11	$50.10	$50.10
Purchase #5	$35.92	9.873%	$39.4664	$39.47	$39.45	$39.50
Purchase #6	$210.79	6.190%	$223.8379	$223.84	$223.85	$223.80
Purchase #7	$129.67	11.438%	$144.5017	$144.50	$144.50	$144.50
7 purchase totals =	$686.42		$747.8673	$747.87	$747.85	$747.90