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	$236.38	9.215%	$258.1624	$258.16	$258.15	$258.20
Purchase #2	$155.97	6.177%	$165.6043	$165.60	$165.60	$165.60
Purchase #3	$157.71	3.163%	$162.6984	$162.70	$162.70	$162.70
Purchase #4	$89.65	6.722%	$95.6763	$95.68	$95.70	$95.70
Purchase #5	$76.37	9.827%	$83.8749	$83.87	$83.85	$83.90
Purchase #6	$192.50	12.488%	$216.5394	$216.54	$216.55	$216.50
Purchase #7	$38.28	12.110%	$42.9157	$42.92	$42.90	$42.90
7 purchase totals =	$946.86		$1,025.4714	$1,025.47	$1,025.45	$1,025.50