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	$94.55	11.712%	$105.6237	$105.62	$105.60	$105.60
Purchase #2	$153.92	8.599%	$167.1556	$167.16	$167.15	$167.20
Purchase #3	$138.98	9.604%	$152.3276	$152.33	$152.35	$152.30
Purchase #4	$83.79	11.612%	$93.5197	$93.52	$93.50	$93.50
Purchase #5	$133.83	13.366%	$151.7177	$151.72	$151.70	$151.70
Purchase #6	$247.92	13.545%	$281.5008	$281.50	$281.50	$281.50
Purchase #7	$181.52	3.814%	$188.4432	$188.44	$188.45	$188.40
7 purchase totals =	$1,034.51		$1,140.2883	$1,140.29	$1,140.25	$1,140.20