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	$96.37	9.519%	$105.5435	$105.54	$105.55	$105.50
Purchase #2	$132.43	12.176%	$148.5547	$148.55	$148.55	$148.60
Purchase #3	$29.69	12.677%	$33.4538	$33.45	$33.45	$33.50
Purchase #4	$99.34	5.130%	$104.4361	$104.44	$104.45	$104.40
Purchase #5	$170.90	7.652%	$183.9773	$183.98	$184.00	$184.00
Purchase #6	$99.60	10.762%	$110.319	$110.32	$110.30	$110.30
Purchase #7	$189.62	5.761%	$200.544	$200.54	$200.55	$200.50
7 purchase totals =	$817.95		$886.8284	$886.82	$886.85	$886.80