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	$129.94	11.863%	$145.3548	$145.35	$145.35	$145.40
Purchase #2	$181.48	8.364%	$196.659	$196.66	$196.65	$196.70
Purchase #3	$13.69	13.131%	$15.4876	$15.49	$15.50	$15.50
Purchase #4	$127.70	4.578%	$133.5461	$133.55	$133.55	$133.50
Purchase #5	$151.79	6.863%	$162.2073	$162.21	$162.20	$162.20
Purchase #6	$106.98	3.862%	$111.1116	$111.11	$111.10	$111.10
Purchase #7	$147.91	7.242%	$158.6216	$158.62	$158.60	$158.60
7 purchase totals =	$859.49		$922.9880	$922.99	$922.95	$923.00