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	$108.94	9.643%	$119.4451	$119.45	$119.45	$119.40
Purchase #2	$218.31	6.374%	$232.2251	$232.23	$232.25	$232.20
Purchase #3	$196.32	11.316%	$218.5356	$218.54	$218.55	$218.50
Purchase #4	$153.72	12.655%	$173.1733	$173.17	$173.15	$173.20
Purchase #5	$215.90	12.593%	$243.0883	$243.09	$243.10	$243.10
Purchase #6	$27.38	5.699%	$28.9404	$28.94	$28.95	$28.90
Purchase #7	$138.61	9.769%	$152.1508	$152.15	$152.15	$152.20
7 purchase totals =	$1,059.18		$1,167.5586	$1,167.57	$1,167.60	$1,167.50