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	$44.98	12.484%	$50.5953	$50.60	$50.60	$50.60
Purchase #2	$13.72	7.390%	$14.7339	$14.73	$14.75	$14.70
Purchase #3	$103.69	7.345%	$111.306	$111.31	$111.30	$111.30
Purchase #4	$12.60	3.805%	$13.0794	$13.08	$13.10	$13.10
Purchase #5	$230.42	8.628%	$250.3006	$250.30	$250.30	$250.30
Purchase #6	$230.65	3.262%	$238.1738	$238.17	$238.15	$238.20
Purchase #7	$24.91	13.668%	$28.3147	$28.31	$28.30	$28.30
7 purchase totals =	$660.97		$706.5037	$706.50	$706.50	$706.50