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	$52.76	12.628%	$59.4225	$59.42	$59.40	$59.40
Purchase #2	$18.36	11.151%	$20.4073	$20.41	$20.40	$20.40
Purchase #3	$27.63	5.344%	$29.1065	$29.11	$29.10	$29.10
Purchase #4	$83.38	3.448%	$86.2549	$86.25	$86.25	$86.30
Purchase #5	$201.68	7.184%	$216.1687	$216.17	$216.15	$216.20
Purchase #6	$50.28	9.564%	$55.0888	$55.09	$55.10	$55.10
Purchase #7	$11.94	13.287%	$13.5265	$13.53	$13.55	$13.50
7 purchase totals =	$446.03		$479.9752	$479.98	$479.95	$480.00