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	$52.95	11.624%	$59.1049	$59.10	$59.10	$59.10
Purchase #2	$83.66	7.731%	$90.1278	$90.13	$90.15	$90.10
Purchase #3	$209.74	12.345%	$235.6324	$235.63	$235.65	$235.60
Purchase #4	$179.40	11.603%	$200.2158	$200.22	$200.20	$200.20
Purchase #5	$154.78	9.431%	$169.3773	$169.38	$169.40	$169.40
Purchase #6	$172.87	6.165%	$183.5274	$183.53	$183.55	$183.50
Purchase #7	$146.87	7.720%	$158.2084	$158.21	$158.20	$158.20
7 purchase totals =	$1,000.27		$1,096.1940	$1,096.20	$1,096.25	$1,096.10