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	$39.41	11.415%	$43.9087	$43.91	$43.90	$43.90
Purchase #2	$37.66	3.788%	$39.0866	$39.09	$39.10	$39.10
Purchase #3	$229.42	9.604%	$251.4535	$251.45	$251.45	$251.50
Purchase #4	$218.55	11.206%	$243.0407	$243.04	$243.05	$243.00
Purchase #5	$197.34	8.488%	$214.0902	$214.09	$214.10	$214.10
Purchase #6	$218.47	5.526%	$230.5427	$230.54	$230.55	$230.50
Purchase #7	$156.60	11.495%	$174.6012	$174.60	$174.60	$174.60
7 purchase totals =	$1,097.45		$1,196.7236	$1,196.72	$1,196.75	$1,196.70