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	$48.59	9.738%	$53.3217	$53.32	$53.30	$53.30
Purchase #2	$198.79	11.362%	$221.3765	$221.38	$221.40	$221.40
Purchase #3	$132.53	13.186%	$150.0054	$150.01	$150.00	$150.00
Purchase #4	$96.69	9.202%	$105.5874	$105.59	$105.60	$105.60
Purchase #5	$236.25	7.552%	$254.0916	$254.09	$254.10	$254.10
Purchase #6	$216.28	12.462%	$243.2328	$243.23	$243.25	$243.20
Purchase #7	$103.84	4.755%	$108.7776	$108.78	$108.80	$108.80
7 purchase totals =	$1,032.97		$1,136.3930	$1,136.40	$1,136.45	$1,136.40