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	$167.89	5.376%	$176.9158	$176.92	$176.90	$176.90
Purchase #2	$187.45	11.654%	$209.2954	$209.30	$209.30	$209.30
Purchase #3	$45.37	3.233%	$46.8368	$46.84	$46.85	$46.80
Purchase #4	$44.30	3.623%	$45.905	$45.91	$45.90	$45.90
Purchase #5	$116.62	5.819%	$123.4061	$123.41	$123.40	$123.40
Purchase #6	$133.39	7.692%	$143.6504	$143.65	$143.65	$143.70
Purchase #7	$205.47	12.130%	$230.3935	$230.39	$230.40	$230.40
7 purchase totals =	$900.49		$976.4030	$976.42	$976.40	$976.40