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	$166.91	8.754%	$181.5213	$181.52	$181.50	$181.50
Purchase #2	$137.35	7.623%	$147.8202	$147.82	$147.80	$147.80
Purchase #3	$47.88	8.708%	$52.0494	$52.05	$52.05	$52.00
Purchase #4	$213.38	11.614%	$238.162	$238.16	$238.15	$238.20
Purchase #5	$140.56	3.261%	$145.1437	$145.14	$145.15	$145.10
Purchase #6	$79.99	13.666%	$90.9214	$90.92	$90.90	$90.90
Purchase #7	$101.28	7.864%	$109.2447	$109.24	$109.25	$109.20
7 purchase totals =	$887.35		$964.8627	$964.85	$964.80	$964.70