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	$180.78	7.187%	$193.7727	$193.77	$193.75	$193.80
Purchase #2	$86.34	4.299%	$90.0518	$90.05	$90.05	$90.10
Purchase #3	$90.74	10.849%	$100.5844	$100.58	$100.60	$100.60
Purchase #4	$159.41	5.161%	$167.6372	$167.64	$167.65	$167.60
Purchase #5	$242.30	11.712%	$270.6782	$270.68	$270.70	$270.70
Purchase #6	$29.92	4.339%	$31.2182	$31.22	$31.20	$31.20
Purchase #7	$158.39	13.679%	$180.0562	$180.06	$180.05	$180.10
7 purchase totals =	$947.88		$1,033.9987	$1,034.00	$1,034.00	$1,034.10