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	$72.80	5.678%	$76.9336	$76.93	$76.95	$76.90
Purchase #2	$117.28	5.368%	$123.5756	$123.58	$123.60	$123.60
Purchase #3	$59.99	11.469%	$66.8703	$66.87	$66.85	$66.90
Purchase #4	$37.43	13.651%	$42.5396	$42.54	$42.55	$42.50
Purchase #5	$174.45	9.117%	$190.3546	$190.35	$190.35	$190.40
Purchase #6	$41.44	3.405%	$42.851	$42.85	$42.85	$42.90
Purchase #7	$242.57	3.381%	$250.7713	$250.77	$250.75	$250.80
7 purchase totals =	$745.96		$793.8960	$793.89	$793.90	$794.00