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	$162.40	10.721%	$179.8109	$179.81	$179.80	$179.80
Purchase #2	$45.51	3.312%	$47.0173	$47.02	$47.00	$47.00
Purchase #3	$36.31	8.702%	$39.4697	$39.47	$39.45	$39.50
Purchase #4	$166.70	5.230%	$175.4184	$175.42	$175.40	$175.40
Purchase #5	$111.55	10.445%	$123.2014	$123.20	$123.20	$123.20
Purchase #6	$140.67	3.335%	$145.3613	$145.36	$145.35	$145.40
Purchase #7	$160.33	3.196%	$165.4541	$165.45	$165.45	$165.50
7 purchase totals =	$823.47		$875.7331	$875.73	$875.65	$875.80