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	$112.76	9.278%	$123.2219	$123.22	$123.20	$123.20
Purchase #2	$72.26	11.616%	$80.6537	$80.65	$80.65	$80.70
Purchase #3	$213.69	4.256%	$222.7846	$222.78	$222.80	$222.80
Purchase #4	$79.77	7.369%	$85.6483	$85.65	$85.65	$85.60
Purchase #5	$234.92	9.657%	$257.6062	$257.61	$257.60	$257.60
Purchase #6	$93.41	10.810%	$103.5076	$103.51	$103.50	$103.50
Purchase #7	$176.72	6.629%	$188.4348	$188.43	$188.45	$188.40
7 purchase totals =	$983.53		$1,061.8571	$1,061.85	$1,061.85	$1,061.80