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	$105.82	5.393%	$111.5269	$111.53	$111.55	$111.50
Purchase #2	$160.42	12.366%	$180.2575	$180.26	$180.25	$180.30
Purchase #3	$150.54	13.336%	$170.616	$170.62	$170.60	$170.60
Purchase #4	$34.68	4.191%	$36.1334	$36.13	$36.15	$36.10
Purchase #5	$70.72	7.646%	$76.1273	$76.13	$76.15	$76.10
Purchase #6	$222.90	8.797%	$242.5085	$242.51	$242.50	$242.50
Purchase #7	$196.43	4.479%	$205.2281	$205.23	$205.25	$205.20
7 purchase totals =	$941.51		$1,022.3977	$1,022.41	$1,022.45	$1,022.30