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	$85.70	11.698%	$95.7252	$95.73	$95.75	$95.70
Purchase #2	$129.40	13.535%	$146.9143	$146.91	$146.90	$146.90
Purchase #3	$95.48	11.116%	$106.0936	$106.09	$106.10	$106.10
Purchase #4	$69.38	4.243%	$72.3238	$72.32	$72.30	$72.30
Purchase #5	$76.28	7.866%	$82.2802	$82.28	$82.30	$82.30
Purchase #6	$128.76	4.238%	$134.2168	$134.22	$134.20	$134.20
Purchase #7	$148.49	13.547%	$168.6059	$168.61	$168.60	$168.60
7 purchase totals =	$733.49		$806.1598	$806.16	$806.15	$806.10