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	$130.40	10.874%	$144.5797	$144.58	$144.60	$144.60
Purchase #2	$232.59	13.129%	$263.1267	$263.13	$263.15	$263.10
Purchase #3	$176.95	6.871%	$189.1082	$189.11	$189.10	$189.10
Purchase #4	$56.84	9.345%	$62.1517	$62.15	$62.15	$62.20
Purchase #5	$21.88	10.312%	$24.1363	$24.14	$24.15	$24.10
Purchase #6	$223.92	3.401%	$231.5355	$231.54	$231.55	$231.50
Purchase #7	$47.85	12.555%	$53.8576	$53.86	$53.85	$53.90
7 purchase totals =	$890.43		$968.4957	$968.51	$968.55	$968.50