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	$102.96	9.548%	$112.7906	$112.79	$112.80	$112.80
Purchase #2	$218.70	8.339%	$236.9374	$236.94	$236.95	$236.90
Purchase #3	$9.87	7.613%	$10.6214	$10.62	$10.60	$10.60
Purchase #4	$70.25	3.809%	$72.9258	$72.93	$72.95	$72.90
Purchase #5	$142.39	7.419%	$152.9539	$152.95	$152.95	$153.00
Purchase #6	$63.96	11.598%	$71.3781	$71.38	$71.40	$71.40
Purchase #7	$78.93	6.154%	$83.7874	$83.79	$83.80	$83.80
7 purchase totals =	$687.06		$741.3946	$741.40	$741.45	$741.40