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	$223.37	9.253%	$244.0384	$244.04	$244.05	$244.00
Purchase #2	$91.90	12.706%	$103.5768	$103.58	$103.60	$103.60
Purchase #3	$48.49	12.644%	$54.6211	$54.62	$54.60	$54.60
Purchase #4	$239.28	10.671%	$264.8136	$264.81	$264.80	$264.80
Purchase #5	$46.50	11.370%	$51.7871	$51.79	$51.80	$51.80
Purchase #6	$5.66	12.649%	$6.3759	$6.38	$6.40	$6.40
Purchase #7	$40.58	4.164%	$42.2698	$42.27	$42.25	$42.30
7 purchase totals =	$695.78		$767.4827	$767.49	$767.50	$767.50