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	$118.58	7.510%	$127.4854	$127.49	$127.50	$127.50
Purchase #2	$217.86	3.527%	$225.5439	$225.54	$225.55	$225.50
Purchase #3	$34.99	9.614%	$38.3539	$38.35	$38.35	$38.40
Purchase #4	$19.29	8.654%	$20.9594	$20.96	$20.95	$21.00
Purchase #5	$167.88	8.119%	$181.5102	$181.51	$181.50	$181.50
Purchase #6	$93.85	13.351%	$106.3799	$106.38	$106.40	$106.40
Purchase #7	$103.29	8.539%	$112.1099	$112.11	$112.10	$112.10
7 purchase totals =	$755.74		$812.3426	$812.34	$812.35	$812.40