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	$115.88	9.128%	$126.4575	$126.46	$126.45	$126.50
Purchase #2	$85.71	3.848%	$89.0081	$89.01	$89.00	$89.00
Purchase #3	$247.73	13.461%	$281.0769	$281.08	$281.10	$281.10
Purchase #4	$148.96	12.194%	$167.1242	$167.12	$167.10	$167.10
Purchase #5	$167.93	3.185%	$173.2786	$173.28	$173.30	$173.30
Purchase #6	$170.46	11.410%	$189.9095	$189.91	$189.90	$189.90
Purchase #7	$38.52	11.790%	$43.0615	$43.06	$43.05	$43.10
7 purchase totals =	$975.19		$1,069.9163	$1,069.92	$1,069.90	$1,070.00