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	$219.35	5.168%	$230.686	$230.69	$230.70	$230.70
Purchase #2	$140.37	11.427%	$156.4101	$156.41	$156.40	$156.40
Purchase #3	$169.41	3.831%	$175.9001	$175.90	$175.90	$175.90
Purchase #4	$196.88	13.279%	$223.0237	$223.02	$223.00	$223.00
Purchase #5	$120.51	6.128%	$127.8949	$127.89	$127.90	$127.90
Purchase #6	$132.91	5.514%	$140.2387	$140.24	$140.25	$140.20
Purchase #7	$9.91	3.108%	$10.218	$10.22	$10.20	$10.20
7 purchase totals =	$989.34		$1,064.3715	$1,064.37	$1,064.35	$1,064.30