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	$82.99	7.552%	$89.2574	$89.26	$89.25	$89.30
Purchase #2	$138.33	8.618%	$150.2513	$150.25	$150.25	$150.30
Purchase #3	$70.47	10.508%	$77.875	$77.88	$77.90	$77.90
Purchase #4	$240.48	6.727%	$256.6571	$256.66	$256.65	$256.70
Purchase #5	$95.35	4.695%	$99.8267	$99.83	$99.85	$99.80
Purchase #6	$48.49	3.437%	$50.1566	$50.16	$50.15	$50.20
Purchase #7	$9.81	11.613%	$10.9492	$10.95	$10.95	$10.90
7 purchase totals =	$685.92		$734.9733	$734.99	$735.00	$735.10