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	$45.63	6.199%	$48.4586	$48.46	$48.45	$48.50
Purchase #2	$250.92	7.339%	$269.335	$269.34	$269.35	$269.30
Purchase #3	$183.41	10.812%	$203.2403	$203.24	$203.25	$203.20
Purchase #4	$228.37	11.689%	$255.0642	$255.06	$255.05	$255.10
Purchase #5	$241.82	13.810%	$275.2153	$275.22	$275.20	$275.20
Purchase #6	$74.28	5.441%	$78.3216	$78.32	$78.30	$78.30
Purchase #7	$86.61	8.249%	$93.7545	$93.75	$93.75	$93.80
7 purchase totals =	$1,111.04		$1,223.3895	$1,223.39	$1,223.35	$1,223.40