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	$233.30	4.872%	$244.6664	$244.67	$244.65	$244.70
Purchase #2	$105.41	5.756%	$111.4774	$111.48	$111.50	$111.50
Purchase #3	$95.48	8.538%	$103.6321	$103.63	$103.65	$103.60
Purchase #4	$116.31	6.722%	$124.1284	$124.13	$124.15	$124.10
Purchase #5	$102.65	9.487%	$112.3884	$112.39	$112.40	$112.40
Purchase #6	$136.57	7.823%	$147.2539	$147.25	$147.25	$147.30
Purchase #7	$105.34	7.411%	$113.1467	$113.15	$113.15	$113.10
7 purchase totals =	$895.06		$956.6933	$956.70	$956.75	$956.70