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	$98.82	10.807%	$109.4995	$109.50	$109.50	$109.50
Purchase #2	$12.76	11.119%	$14.1788	$14.18	$14.20	$14.20
Purchase #3	$172.88	13.874%	$196.8654	$196.87	$196.85	$196.90
Purchase #4	$244.84	10.347%	$270.1736	$270.17	$270.15	$270.20
Purchase #5	$167.95	6.544%	$178.9406	$178.94	$178.95	$178.90
Purchase #6	$23.49	13.300%	$26.6142	$26.61	$26.60	$26.60
Purchase #7	$98.37	13.186%	$111.3411	$111.34	$111.35	$111.30
7 purchase totals =	$819.11		$907.6132	$907.61	$907.60	$907.60