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	$228.33	4.369%	$238.3057	$238.31	$238.30	$238.30
Purchase #2	$43.40	4.761%	$45.4663	$45.47	$45.45	$45.50
Purchase #3	$123.96	7.428%	$133.1677	$133.17	$133.15	$133.20
Purchase #4	$81.25	10.253%	$89.5806	$89.58	$89.60	$89.60
Purchase #5	$85.51	8.609%	$92.8716	$92.87	$92.85	$92.90
Purchase #6	$106.65	13.808%	$121.3762	$121.38	$121.40	$121.40
Purchase #7	$132.27	6.160%	$140.4178	$140.42	$140.40	$140.40
7 purchase totals =	$801.37		$861.1859	$861.20	$861.15	$861.30