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	$111.64	13.423%	$126.6254	$126.63	$126.65	$126.60
Purchase #2	$41.37	10.215%	$45.5959	$45.60	$45.60	$45.60
Purchase #3	$71.29	10.232%	$78.5844	$78.58	$78.60	$78.60
Purchase #4	$118.90	12.608%	$133.8909	$133.89	$133.90	$133.90
Purchase #5	$171.41	12.108%	$192.1643	$192.16	$192.15	$192.20
Purchase #6	$185.93	10.662%	$205.7539	$205.75	$205.75	$205.80
Purchase #7	$85.36	4.168%	$88.9178	$88.92	$88.90	$88.90
7 purchase totals =	$785.90		$871.5326	$871.53	$871.55	$871.60