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	$144.31	4.731%	$151.1373	$151.14	$151.15	$151.10
Purchase #2	$232.78	12.476%	$261.8216	$261.82	$261.80	$261.80
Purchase #3	$99.30	5.183%	$104.4467	$104.45	$104.45	$104.40
Purchase #4	$176.55	4.556%	$184.5936	$184.59	$184.60	$184.60
Purchase #5	$242.61	5.500%	$255.9536	$255.95	$255.95	$256.00
Purchase #6	$65.54	11.120%	$72.828	$72.83	$72.85	$72.80
Purchase #7	$186.93	13.860%	$212.8385	$212.84	$212.85	$212.80
7 purchase totals =	$1,148.02		$1,243.6193	$1,243.62	$1,243.65	$1,243.50