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	$219.45	10.400%	$242.2728	$242.27	$242.25	$242.30
Purchase #2	$107.56	6.538%	$114.5923	$114.59	$114.60	$114.60
Purchase #3	$146.29	3.829%	$151.8914	$151.89	$151.90	$151.90
Purchase #4	$195.84	3.534%	$202.761	$202.76	$202.75	$202.80
Purchase #5	$210.87	10.558%	$233.1337	$233.13	$233.15	$233.10
Purchase #6	$197.85	13.133%	$223.8336	$223.83	$223.85	$223.80
Purchase #7	$92.75	8.211%	$100.3657	$100.37	$100.35	$100.40
7 purchase totals =	$1,170.61		$1,268.8505	$1,268.84	$1,268.85	$1,268.90