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	$247.70	6.523%	$263.8575	$263.86	$263.85	$263.90
Purchase #2	$205.62	10.146%	$226.4822	$226.48	$226.50	$226.50
Purchase #3	$38.81	4.150%	$40.4206	$40.42	$40.40	$40.40
Purchase #4	$104.58	6.612%	$111.4948	$111.49	$111.50	$111.50
Purchase #5	$246.26	9.353%	$269.2927	$269.29	$269.30	$269.30
Purchase #6	$124.35	9.603%	$136.2913	$136.29	$136.30	$136.30
Purchase #7	$176.57	7.799%	$190.3407	$190.34	$190.35	$190.30
7 purchase totals =	$1,143.89		$1,238.1798	$1,238.17	$1,238.20	$1,238.20