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	$173.39	11.556%	$193.4269	$193.43	$193.45	$193.40
Purchase #2	$102.50	8.471%	$111.1828	$111.18	$111.20	$111.20
Purchase #3	$167.89	4.589%	$175.5945	$175.59	$175.60	$175.60
Purchase #4	$160.34	6.456%	$170.6916	$170.69	$170.70	$170.70
Purchase #5	$221.68	12.429%	$249.2326	$249.23	$249.25	$249.20
Purchase #6	$238.36	13.708%	$271.0344	$271.03	$271.05	$271.00
Purchase #7	$148.32	13.384%	$168.1711	$168.17	$168.15	$168.20
7 purchase totals =	$1,212.48		$1,339.3339	$1,339.32	$1,339.40	$1,339.30