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	$236.57	4.164%	$246.4208	$246.42	$246.40	$246.40
Purchase #2	$72.96	13.274%	$82.6447	$82.64	$82.65	$82.60
Purchase #3	$38.96	4.247%	$40.6146	$40.61	$40.60	$40.60
Purchase #4	$68.60	11.144%	$76.2448	$76.24	$76.25	$76.20
Purchase #5	$13.78	13.331%	$15.617	$15.62	$15.60	$15.60
Purchase #6	$50.52	5.283%	$53.189	$53.19	$53.20	$53.20
Purchase #7	$188.65	11.792%	$210.8956	$210.90	$210.90	$210.90
7 purchase totals =	$670.04		$725.6265	$725.62	$725.60	$725.50