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	$250.61	6.864%	$267.8119	$267.81	$267.80	$267.80
Purchase #2	$37.42	11.154%	$41.5938	$41.59	$41.60	$41.60
Purchase #3	$29.81	7.350%	$32.001	$32.00	$32.00	$32.00
Purchase #4	$60.54	9.781%	$66.4614	$66.46	$66.45	$66.50
Purchase #5	$34.53	9.636%	$37.8573	$37.86	$37.85	$37.90
Purchase #6	$153.53	13.686%	$174.5421	$174.54	$174.55	$174.50
Purchase #7	$53.44	13.734%	$60.7794	$60.78	$60.80	$60.80
7 purchase totals =	$619.88		$681.0469	$681.04	$681.05	$681.10