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	$108.63	3.325%	$112.2419	$112.24	$112.25	$112.20
Purchase #2	$235.89	8.235%	$255.3155	$255.32	$255.30	$255.30
Purchase #3	$225.86	6.796%	$241.2094	$241.21	$241.20	$241.20
Purchase #4	$36.32	3.827%	$37.71	$37.71	$37.70	$37.70
Purchase #5	$215.92	3.287%	$223.0173	$223.02	$223.00	$223.00
Purchase #6	$66.97	10.224%	$73.817	$73.82	$73.80	$73.80
Purchase #7	$62.91	5.433%	$66.3279	$66.33	$66.35	$66.30
7 purchase totals =	$952.50		$1,009.6390	$1,009.65	$1,009.60	$1,009.50