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	$197.88	10.238%	$218.139	$218.14	$218.15	$218.10
Purchase #2	$135.79	9.595%	$148.8191	$148.82	$148.80	$148.80
Purchase #3	$90.94	9.522%	$99.5993	$99.60	$99.60	$99.60
Purchase #4	$117.58	8.193%	$127.2133	$127.21	$127.20	$127.20
Purchase #5	$170.52	10.688%	$188.7452	$188.75	$188.75	$188.70
Purchase #6	$187.89	9.614%	$205.9537	$205.95	$205.95	$206.00
Purchase #7	$131.51	6.381%	$139.9017	$139.90	$139.90	$139.90
7 purchase totals =	$1,032.11		$1,128.3713	$1,128.37	$1,128.35	$1,128.30