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	$177.60	5.725%	$187.7676	$187.77	$187.75	$187.80
Purchase #2	$146.32	3.405%	$151.3022	$151.30	$151.30	$151.30
Purchase #3	$8.29	6.219%	$8.8056	$8.81	$8.80	$8.80
Purchase #4	$81.88	10.200%	$90.2318	$90.23	$90.25	$90.20
Purchase #5	$92.42	7.699%	$99.5354	$99.54	$99.55	$99.50
Purchase #6	$136.56	3.273%	$141.0296	$141.03	$141.05	$141.00
Purchase #7	$92.37	4.298%	$96.3401	$96.34	$96.35	$96.30
7 purchase totals =	$735.44		$775.0123	$775.02	$775.05	$774.90