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	$218.80	6.463%	$232.941	$232.94	$232.95	$232.90
Purchase #2	$139.47	3.785%	$144.7489	$144.75	$144.75	$144.70
Purchase #3	$112.82	13.485%	$128.0338	$128.03	$128.05	$128.00
Purchase #4	$57.39	4.295%	$59.8549	$59.85	$59.85	$59.90
Purchase #5	$19.61	11.715%	$21.9073	$21.91	$21.90	$21.90
Purchase #6	$179.40	5.300%	$188.9082	$188.91	$188.90	$188.90
Purchase #7	$158.92	3.216%	$164.0309	$164.03	$164.05	$164.00
7 purchase totals =	$886.41		$940.4250	$940.42	$940.45	$940.30