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	$106.92	4.872%	$112.1291	$112.13	$112.15	$112.10
Purchase #2	$29.41	12.309%	$33.0301	$33.03	$33.05	$33.00
Purchase #3	$173.71	7.130%	$186.0955	$186.10	$186.10	$186.10
Purchase #4	$143.73	4.598%	$150.3387	$150.34	$150.35	$150.30
Purchase #5	$160.81	7.179%	$172.3545	$172.35	$172.35	$172.40
Purchase #6	$11.54	4.709%	$12.0834	$12.08	$12.10	$12.10
Purchase #7	$116.86	4.693%	$122.3442	$122.34	$122.35	$122.30
7 purchase totals =	$742.98		$788.3755	$788.37	$788.45	$788.30