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	$165.66	4.526%	$173.1578	$173.16	$173.15	$173.20
Purchase #2	$21.76	11.622%	$24.2889	$24.29	$24.30	$24.30
Purchase #3	$244.84	13.197%	$277.1515	$277.15	$277.15	$277.20
Purchase #4	$81.77	4.652%	$85.5739	$85.57	$85.55	$85.60
Purchase #5	$226.40	10.799%	$250.8489	$250.85	$250.85	$250.80
Purchase #6	$142.68	9.747%	$156.587	$156.59	$156.60	$156.60
Purchase #7	$93.57	6.468%	$99.6221	$99.62	$99.60	$99.60
7 purchase totals =	$976.68		$1,067.2301	$1,067.23	$1,067.20	$1,067.30