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	$48.47	4.118%	$50.466	$50.47	$50.45	$50.50
Purchase #2	$180.57	13.623%	$205.1691	$205.17	$205.15	$205.20
Purchase #3	$102.59	13.322%	$116.257	$116.26	$116.25	$116.30
Purchase #4	$250.27	3.231%	$258.3562	$258.36	$258.35	$258.40
Purchase #5	$37.46	8.819%	$40.7636	$40.76	$40.75	$40.80
Purchase #6	$216.39	8.174%	$234.0777	$234.08	$234.10	$234.10
Purchase #7	$85.68	13.415%	$97.174	$97.17	$97.15	$97.20
7 purchase totals =	$921.43		$1,002.2636	$1,002.27	$1,002.20	$1,002.50