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	$118.78	6.233%	$126.1836	$126.18	$126.20	$126.20
Purchase #2	$160.96	4.342%	$167.9489	$167.95	$167.95	$167.90
Purchase #3	$115.70	10.173%	$127.4702	$127.47	$127.45	$127.50
Purchase #4	$55.43	10.514%	$61.2579	$61.26	$61.25	$61.30
Purchase #5	$170.71	7.673%	$183.8086	$183.81	$183.80	$183.80
Purchase #6	$71.61	12.334%	$80.4424	$80.44	$80.45	$80.40
Purchase #7	$34.59	13.816%	$39.369	$39.37	$39.35	$39.40
7 purchase totals =	$727.78		$786.4806	$786.48	$786.45	$786.50