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	$82.46	10.429%	$91.0598	$91.06	$91.05	$91.10
Purchase #2	$122.99	12.120%	$137.8964	$137.90	$137.90	$137.90
Purchase #3	$100.29	3.217%	$103.5163	$103.52	$103.50	$103.50
Purchase #4	$247.52	13.589%	$281.1555	$281.16	$281.15	$281.20
Purchase #5	$157.57	6.369%	$167.6056	$167.61	$167.60	$167.60
Purchase #6	$183.41	11.303%	$204.1408	$204.14	$204.15	$204.10
Purchase #7	$28.49	12.547%	$32.0646	$32.06	$32.05	$32.10
7 purchase totals =	$922.73		$1,017.4390	$1,017.45	$1,017.40	$1,017.50