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	$225.30	9.808%	$247.3974	$247.40	$247.40	$247.40
Purchase #2	$123.90	5.304%	$130.4717	$130.47	$130.45	$130.50
Purchase #3	$17.57	3.726%	$18.2247	$18.22	$18.20	$18.20
Purchase #4	$138.53	9.800%	$152.1059	$152.11	$152.10	$152.10
Purchase #5	$79.88	11.600%	$89.1461	$89.15	$89.15	$89.10
Purchase #6	$129.55	7.752%	$139.5927	$139.59	$139.60	$139.60
Purchase #7	$200.62	12.327%	$225.3504	$225.35	$225.35	$225.40
7 purchase totals =	$915.35		$1,002.2889	$1,002.29	$1,002.25	$1,002.30