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	$130.94	7.862%	$141.2345	$141.23	$141.25	$141.20
Purchase #2	$139.73	9.724%	$153.3173	$153.32	$153.30	$153.30
Purchase #3	$25.55	11.240%	$28.4218	$28.42	$28.40	$28.40
Purchase #4	$40.34	8.535%	$43.783	$43.78	$43.80	$43.80
Purchase #5	$196.81	3.281%	$203.2673	$203.27	$203.25	$203.30
Purchase #6	$145.92	3.760%	$151.4066	$151.41	$151.40	$151.40
Purchase #7	$203.25	11.263%	$226.142	$226.14	$226.15	$226.10
7 purchase totals =	$882.54		$947.5725	$947.57	$947.55	$947.50