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	$173.85	13.811%	$197.8604	$197.86	$197.85	$197.90
Purchase #2	$82.61	9.659%	$90.5893	$90.59	$90.60	$90.60
Purchase #3	$152.55	6.253%	$162.089	$162.09	$162.10	$162.10
Purchase #4	$188.28	3.246%	$194.3916	$194.39	$194.40	$194.40
Purchase #5	$37.62	9.205%	$41.0829	$41.08	$41.10	$41.10
Purchase #6	$87.78	4.569%	$91.7907	$91.79	$91.80	$91.80
Purchase #7	$99.29	9.248%	$108.4723	$108.47	$108.45	$108.50
7 purchase totals =	$821.98		$886.2762	$886.27	$886.30	$886.40