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	$48.91	3.572%	$50.6571	$50.66	$50.65	$50.70
Purchase #2	$196.66	6.102%	$208.6602	$208.66	$208.65	$208.70
Purchase #3	$94.94	5.719%	$100.3696	$100.37	$100.35	$100.40
Purchase #4	$124.35	11.334%	$138.4438	$138.44	$138.45	$138.40
Purchase #5	$145.96	13.126%	$165.1187	$165.12	$165.10	$165.10
Purchase #6	$150.95	12.745%	$170.1886	$170.19	$170.20	$170.20
Purchase #7	$175.57	5.847%	$185.8356	$185.84	$185.85	$185.80
7 purchase totals =	$937.34		$1,019.2736	$1,019.28	$1,019.25	$1,019.30