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	$146.68	12.714%	$165.3289	$165.33	$165.35	$165.30
Purchase #2	$214.69	7.653%	$231.1202	$231.12	$231.10	$231.10
Purchase #3	$134.79	12.717%	$151.9312	$151.93	$151.95	$151.90
Purchase #4	$185.30	5.713%	$195.8862	$195.89	$195.90	$195.90
Purchase #5	$83.80	7.466%	$90.0565	$90.06	$90.05	$90.10
Purchase #6	$105.29	6.567%	$112.2044	$112.20	$112.20	$112.20
Purchase #7	$110.59	11.288%	$123.0734	$123.07	$123.05	$123.10
7 purchase totals =	$981.14		$1,069.6008	$1,069.60	$1,069.60	$1,069.60