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	$140.61	13.255%	$159.2479	$159.25	$159.25	$159.20
Purchase #2	$224.29	9.620%	$245.8667	$245.87	$245.85	$245.90
Purchase #3	$33.53	11.161%	$37.2723	$37.27	$37.25	$37.30
Purchase #4	$158.32	7.750%	$170.5898	$170.59	$170.60	$170.60
Purchase #5	$211.94	6.189%	$225.057	$225.06	$225.05	$225.10
Purchase #6	$148.84	10.776%	$164.879	$164.88	$164.90	$164.90
Purchase #7	$183.89	5.191%	$193.4357	$193.44	$193.45	$193.40
7 purchase totals =	$1,101.42		$1,196.3484	$1,196.36	$1,196.35	$1,196.40