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	$169.85	9.575%	$186.1131	$186.11	$186.10	$186.10
Purchase #2	$153.56	9.218%	$167.7152	$167.72	$167.70	$167.70
Purchase #3	$244.36	13.222%	$276.6693	$276.67	$276.65	$276.70
Purchase #4	$161.46	7.626%	$173.7729	$173.77	$173.75	$173.80
Purchase #5	$166.69	8.758%	$181.2887	$181.29	$181.30	$181.30
Purchase #6	$113.49	8.773%	$123.4465	$123.45	$123.45	$123.40
Purchase #7	$159.49	3.140%	$164.498	$164.50	$164.50	$164.50
7 purchase totals =	$1,168.90		$1,273.5037	$1,273.51	$1,273.45	$1,273.50