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	$104.48	6.380%	$111.1458	$111.15	$111.15	$111.10
Purchase #2	$18.59	11.265%	$20.6842	$20.68	$20.70	$20.70
Purchase #3	$102.84	9.235%	$112.3373	$112.34	$112.35	$112.30
Purchase #4	$104.48	6.110%	$110.8637	$110.86	$110.85	$110.90
Purchase #5	$153.28	3.400%	$158.4915	$158.49	$158.50	$158.50
Purchase #6	$101.41	7.658%	$109.176	$109.18	$109.20	$109.20
Purchase #7	$87.41	9.434%	$95.6563	$95.66	$95.65	$95.70
7 purchase totals =	$672.49		$718.3548	$718.36	$718.40	$718.40