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	$183.72	6.772%	$196.1615	$196.16	$196.15	$196.20
Purchase #2	$23.53	3.713%	$24.4037	$24.40	$24.40	$24.40
Purchase #3	$181.82	4.684%	$190.3364	$190.34	$190.35	$190.30
Purchase #4	$42.64	6.102%	$45.2419	$45.24	$45.25	$45.20
Purchase #5	$157.75	9.743%	$173.1196	$173.12	$173.10	$173.10
Purchase #6	$71.98	13.380%	$81.6109	$81.61	$81.60	$81.60
Purchase #7	$44.31	13.745%	$50.4004	$50.40	$50.40	$50.40
7 purchase totals =	$705.75		$761.2744	$761.27	$761.25	$761.20