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	$103.91	7.273%	$111.4674	$111.47	$111.45	$111.50
Purchase #2	$48.75	7.874%	$52.5886	$52.59	$52.60	$52.60
Purchase #3	$235.26	4.267%	$245.2985	$245.30	$245.30	$245.30
Purchase #4	$136.73	13.223%	$154.8098	$154.81	$154.80	$154.80
Purchase #5	$241.47	9.639%	$264.7453	$264.75	$264.75	$264.70
Purchase #6	$130.84	4.822%	$137.1491	$137.15	$137.15	$137.10
Purchase #7	$18.68	7.439%	$20.0696	$20.07	$20.05	$20.10
7 purchase totals =	$915.64		$986.1283	$986.14	$986.10	$986.10