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	$85.31	4.219%	$88.9092	$88.91	$88.90	$88.90
Purchase #2	$19.84	4.634%	$20.7594	$20.76	$20.75	$20.80
Purchase #3	$194.42	5.680%	$205.4631	$205.46	$205.45	$205.50
Purchase #4	$208.96	3.445%	$216.1587	$216.16	$216.15	$216.20
Purchase #5	$232.66	11.262%	$258.8622	$258.86	$258.85	$258.90
Purchase #6	$168.54	5.365%	$177.5822	$177.58	$177.60	$177.60
Purchase #7	$92.25	4.740%	$96.6227	$96.62	$96.60	$96.60
7 purchase totals =	$1,001.98		$1,064.3575	$1,064.35	$1,064.30	$1,064.50