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	$163.55	5.854%	$173.1242	$173.12	$173.10	$173.10
Purchase #2	$238.34	5.523%	$251.5035	$251.50	$251.50	$251.50
Purchase #3	$102.49	8.487%	$111.1883	$111.19	$111.20	$111.20
Purchase #4	$78.35	10.541%	$86.6089	$86.61	$86.60	$86.60
Purchase #5	$46.61	5.604%	$49.222	$49.22	$49.20	$49.20
Purchase #6	$57.73	8.283%	$62.5118	$62.51	$62.50	$62.50
Purchase #7	$245.46	13.476%	$278.5382	$278.54	$278.55	$278.50
7 purchase totals =	$932.53		$1,012.6969	$1,012.69	$1,012.65	$1,012.60