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	$207.74	5.853%	$219.899	$219.90	$219.90	$219.90
Purchase #2	$49.60	9.366%	$54.2455	$54.25	$54.25	$54.20
Purchase #3	$145.76	13.843%	$165.9376	$165.94	$165.95	$165.90
Purchase #4	$38.29	12.621%	$43.1226	$43.12	$43.10	$43.10
Purchase #5	$31.72	13.590%	$36.0307	$36.03	$36.05	$36.00
Purchase #6	$57.95	13.478%	$65.7605	$65.76	$65.75	$65.80
Purchase #7	$28.68	4.264%	$29.9029	$29.90	$29.90	$29.90
7 purchase totals =	$559.74		$614.8988	$614.90	$614.90	$614.80