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	$188.39	5.677%	$199.0849	$199.08	$199.10	$199.10
Purchase #2	$63.41	4.341%	$66.1626	$66.16	$66.15	$66.20
Purchase #3	$203.65	5.643%	$215.142	$215.14	$215.15	$215.10
Purchase #4	$83.57	9.866%	$91.815	$91.82	$91.80	$91.80
Purchase #5	$190.92	6.553%	$203.431	$203.43	$203.45	$203.40
Purchase #6	$127.89	6.814%	$136.6044	$136.60	$136.60	$136.60
Purchase #7	$76.47	7.636%	$82.3092	$82.31	$82.30	$82.30
7 purchase totals =	$934.30		$994.5491	$994.54	$994.55	$994.50