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	$138.36	8.315%	$149.8646	$149.86	$149.85	$149.90
Purchase #2	$47.47	8.246%	$51.3844	$51.38	$51.40	$51.40
Purchase #3	$93.69	8.258%	$101.4269	$101.43	$101.45	$101.40
Purchase #4	$92.60	7.414%	$99.4654	$99.47	$99.45	$99.50
Purchase #5	$151.48	7.193%	$162.376	$162.38	$162.40	$162.40
Purchase #6	$115.93	9.782%	$127.2703	$127.27	$127.25	$127.30
Purchase #7	$188.50	6.109%	$200.0155	$200.02	$200.00	$200.00
7 purchase totals =	$828.03		$891.8031	$891.81	$891.80	$891.90