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	$157.59	8.613%	$171.1632	$171.16	$171.15	$171.20
Purchase #2	$79.82	4.363%	$83.3025	$83.30	$83.30	$83.30
Purchase #3	$10.28	11.533%	$11.4656	$11.47	$11.45	$11.50
Purchase #4	$92.48	3.719%	$95.9193	$95.92	$95.90	$95.90
Purchase #5	$240.37	11.684%	$268.4548	$268.45	$268.45	$268.50
Purchase #6	$91.68	10.210%	$101.0405	$101.04	$101.05	$101.00
Purchase #7	$39.89	3.177%	$41.1573	$41.16	$41.15	$41.20
7 purchase totals =	$712.11		$772.5032	$772.50	$772.45	$772.60