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	$141.89	4.508%	$148.2864	$148.29	$148.30	$148.30
Purchase #2	$195.80	4.850%	$205.2963	$205.30	$205.30	$205.30
Purchase #3	$190.94	9.523%	$209.1232	$209.12	$209.10	$209.10
Purchase #4	$153.86	13.844%	$175.1604	$175.16	$175.15	$175.20
Purchase #5	$37.61	4.830%	$39.4266	$39.43	$39.45	$39.40
Purchase #6	$75.85	6.668%	$80.9077	$80.91	$80.90	$80.90
Purchase #7	$143.33	11.428%	$159.7098	$159.71	$159.70	$159.70
7 purchase totals =	$939.28		$1,017.9104	$1,017.92	$1,017.90	$1,017.90