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	$180.95	6.347%	$192.4349	$192.43	$192.45	$192.40
Purchase #2	$27.84	11.183%	$30.9533	$30.95	$30.95	$31.00
Purchase #3	$190.43	11.810%	$212.9198	$212.92	$212.90	$212.90
Purchase #4	$152.32	4.114%	$158.5864	$158.59	$158.60	$158.60
Purchase #5	$150.80	13.327%	$170.8971	$170.90	$170.90	$170.90
Purchase #6	$193.30	9.621%	$211.8974	$211.90	$211.90	$211.90
Purchase #7	$123.62	6.410%	$131.544	$131.54	$131.55	$131.50
7 purchase totals =	$1,019.26		$1,109.2329	$1,109.23	$1,109.25	$1,109.20