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	$224.98	4.272%	$234.5911	$234.59	$234.60	$234.60
Purchase #2	$62.57	11.148%	$69.5453	$69.55	$69.55	$69.50
Purchase #3	$23.38	3.370%	$24.1679	$24.17	$24.15	$24.20
Purchase #4	$104.31	8.711%	$113.3964	$113.40	$113.40	$113.40
Purchase #5	$101.26	10.201%	$111.5895	$111.59	$111.60	$111.60
Purchase #6	$78.38	4.742%	$82.0968	$82.10	$82.10	$82.10
Purchase #7	$122.59	8.748%	$133.3142	$133.31	$133.30	$133.30
7 purchase totals =	$717.47		$768.7012	$768.71	$768.70	$768.70