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	$129.45	9.196%	$141.3542	$141.35	$141.35	$141.40
Purchase #2	$119.34	6.719%	$127.3585	$127.36	$127.35	$127.40
Purchase #3	$159.37	10.523%	$176.1405	$176.14	$176.15	$176.10
Purchase #4	$52.27	9.696%	$57.3381	$57.34	$57.35	$57.30
Purchase #5	$110.46	3.318%	$114.1251	$114.13	$114.15	$114.10
Purchase #6	$195.85	5.249%	$206.1302	$206.13	$206.15	$206.10
Purchase #7	$226.36	5.461%	$238.7215	$238.72	$238.70	$238.70
7 purchase totals =	$993.10		$1,061.1681	$1,061.17	$1,061.20	$1,061.10