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	$111.86	11.393%	$124.6042	$124.60	$124.60	$124.60
Purchase #2	$57.85	12.676%	$65.1831	$65.18	$65.20	$65.20
Purchase #3	$7.67	12.134%	$8.6007	$8.60	$8.60	$8.60
Purchase #4	$75.62	8.752%	$82.2383	$82.24	$82.25	$82.20
Purchase #5	$95.88	4.759%	$100.4429	$100.44	$100.45	$100.40
Purchase #6	$20.95	4.454%	$21.8831	$21.88	$21.90	$21.90
Purchase #7	$113.98	9.444%	$124.7443	$124.74	$124.75	$124.70
7 purchase totals =	$483.81		$527.6966	$527.68	$527.75	$527.60