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	$143.91	10.232%	$158.6349	$158.63	$158.65	$158.60
Purchase #2	$90.92	4.551%	$95.0578	$95.06	$95.05	$95.10
Purchase #3	$191.44	4.276%	$199.626	$199.63	$199.65	$199.60
Purchase #4	$139.84	9.871%	$153.6436	$153.64	$153.65	$153.60
Purchase #5	$82.42	8.719%	$89.6062	$89.61	$89.60	$89.60
Purchase #6	$38.46	8.315%	$41.6579	$41.66	$41.65	$41.70
Purchase #7	$86.45	10.865%	$95.8428	$95.84	$95.85	$95.80
7 purchase totals =	$773.44		$834.0692	$834.07	$834.10	$834.00