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	$226.79	7.631%	$244.0963	$244.10	$244.10	$244.10
Purchase #2	$155.73	9.497%	$170.5197	$170.52	$170.50	$170.50
Purchase #3	$243.25	12.467%	$273.576	$273.58	$273.60	$273.60
Purchase #4	$12.51	10.494%	$13.8228	$13.82	$13.80	$13.80
Purchase #5	$194.99	5.444%	$205.6053	$205.61	$205.60	$205.60
Purchase #6	$102.62	6.658%	$109.4524	$109.45	$109.45	$109.50
Purchase #7	$148.35	13.815%	$168.8446	$168.84	$168.85	$168.80
7 purchase totals =	$1,084.24		$1,185.9171	$1,185.92	$1,185.90	$1,185.90