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	$86.98	10.829%	$96.3991	$96.40	$96.40	$96.40
Purchase #2	$117.62	12.377%	$132.1778	$132.18	$132.20	$132.20
Purchase #3	$64.53	12.505%	$72.5995	$72.60	$72.60	$72.60
Purchase #4	$34.66	13.437%	$39.3173	$39.32	$39.30	$39.30
Purchase #5	$191.28	11.599%	$213.4666	$213.47	$213.45	$213.50
Purchase #6	$158.26	6.687%	$168.8428	$168.84	$168.85	$168.80
Purchase #7	$35.66	6.132%	$37.8467	$37.85	$37.85	$37.80
7 purchase totals =	$688.99		$760.6498	$760.66	$760.65	$760.60