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	$92.61	13.360%	$104.9827	$104.98	$105.00	$105.00
Purchase #2	$32.48	7.868%	$35.0355	$35.04	$35.05	$35.00
Purchase #3	$95.37	10.806%	$105.6757	$105.68	$105.70	$105.70
Purchase #4	$150.72	5.536%	$159.0639	$159.06	$159.05	$159.10
Purchase #5	$76.74	12.413%	$86.2657	$86.27	$86.25	$86.30
Purchase #6	$239.36	6.693%	$255.3804	$255.38	$255.40	$255.40
Purchase #7	$60.52	7.808%	$65.2454	$65.25	$65.25	$65.20
7 purchase totals =	$747.80		$811.6493	$811.66	$811.70	$811.70