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	$40.39	13.695%	$45.9214	$45.92	$45.90	$45.90
Purchase #2	$89.52	13.483%	$101.59	$101.59	$101.60	$101.60
Purchase #3	$75.72	9.842%	$83.1724	$83.17	$83.15	$83.20
Purchase #4	$238.37	10.301%	$262.9245	$262.92	$262.90	$262.90
Purchase #5	$182.56	11.790%	$204.0838	$204.08	$204.10	$204.10
Purchase #6	$89.86	5.568%	$94.8634	$94.86	$94.85	$94.90
Purchase #7	$92.99	12.277%	$104.4064	$104.41	$104.40	$104.40
7 purchase totals =	$809.41		$896.9619	$896.95	$896.90	$897.00