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	$143.29	3.529%	$148.3467	$148.35	$148.35	$148.30
Purchase #2	$17.56	8.849%	$19.1139	$19.11	$19.10	$19.10
Purchase #3	$165.96	11.679%	$185.3425	$185.34	$185.35	$185.30
Purchase #4	$65.37	7.758%	$70.4414	$70.44	$70.45	$70.40
Purchase #5	$46.67	12.439%	$52.4753	$52.48	$52.50	$52.50
Purchase #6	$50.25	7.666%	$54.1022	$54.10	$54.10	$54.10
Purchase #7	$143.67	10.350%	$158.5398	$158.54	$158.55	$158.50
7 purchase totals =	$632.77		$688.3618	$688.36	$688.40	$688.20