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	$146.48	12.235%	$164.4018	$164.40	$164.40	$164.40
Purchase #2	$94.83	13.477%	$107.6102	$107.61	$107.60	$107.60
Purchase #3	$95.73	10.667%	$105.9415	$105.94	$105.95	$105.90
Purchase #4	$38.56	11.652%	$43.053	$43.05	$43.05	$43.10
Purchase #5	$216.30	9.667%	$237.2097	$237.21	$237.20	$237.20
Purchase #6	$230.33	4.317%	$240.2733	$240.27	$240.25	$240.30
Purchase #7	$69.79	4.350%	$72.8259	$72.83	$72.85	$72.80
7 purchase totals =	$892.02		$971.3154	$971.31	$971.30	$971.30