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	$135.27	9.598%	$148.2532	$148.25	$148.25	$148.30
Purchase #2	$97.72	6.502%	$104.0738	$104.07	$104.05	$104.10
Purchase #3	$192.80	13.728%	$219.2676	$219.27	$219.25	$219.30
Purchase #4	$55.73	7.366%	$59.8351	$59.84	$59.85	$59.80
Purchase #5	$158.35	8.752%	$172.2088	$172.21	$172.20	$172.20
Purchase #6	$51.54	3.829%	$53.5135	$53.51	$53.50	$53.50
Purchase #7	$240.81	7.324%	$258.4469	$258.45	$258.45	$258.40
7 purchase totals =	$932.22		$1,015.5989	$1,015.60	$1,015.55	$1,015.60