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	$141.31	13.389%	$160.23	$160.23	$160.25	$160.20
Purchase #2	$179.73	8.328%	$194.6979	$194.70	$194.70	$194.70
Purchase #3	$14.45	12.127%	$16.2024	$16.20	$16.20	$16.20
Purchase #4	$225.43	12.839%	$254.373	$254.37	$254.35	$254.40
Purchase #5	$49.34	10.691%	$54.6149	$54.61	$54.60	$54.60
Purchase #6	$200.46	11.292%	$223.0959	$223.10	$223.10	$223.10
Purchase #7	$122.60	4.315%	$127.8902	$127.89	$127.90	$127.90
7 purchase totals =	$933.32		$1,031.1043	$1,031.10	$1,031.10	$1,031.10