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	$109.40	5.373%	$115.2781	$115.28	$115.30	$115.30
Purchase #2	$20.27	10.806%	$22.4604	$22.46	$22.45	$22.50
Purchase #3	$191.25	8.164%	$206.8637	$206.86	$206.85	$206.90
Purchase #4	$231.81	8.632%	$251.8198	$251.82	$251.80	$251.80
Purchase #5	$87.86	13.697%	$99.8942	$99.89	$99.90	$99.90
Purchase #6	$81.78	4.540%	$85.4928	$85.49	$85.50	$85.50
Purchase #7	$137.62	10.424%	$151.9655	$151.97	$151.95	$152.00
7 purchase totals =	$859.99		$933.7745	$933.77	$933.75	$933.90