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	$174.35	8.351%	$188.91	$188.91	$188.90	$188.90
Purchase #2	$179.66	10.728%	$198.9339	$198.93	$198.95	$198.90
Purchase #3	$58.81	11.205%	$65.3997	$65.40	$65.40	$65.40
Purchase #4	$17.81	10.122%	$19.6127	$19.61	$19.60	$19.60
Purchase #5	$119.73	5.697%	$126.551	$126.55	$126.55	$126.60
Purchase #6	$86.32	3.332%	$89.1962	$89.20	$89.20	$89.20
Purchase #7	$132.28	10.277%	$145.8744	$145.87	$145.85	$145.90
7 purchase totals =	$768.96		$834.4779	$834.47	$834.45	$834.50