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	$11.71	11.622%	$13.0709	$13.07	$13.05	$13.10
Purchase #2	$77.46	6.526%	$82.515	$82.52	$82.50	$82.50
Purchase #3	$217.71	11.202%	$242.0979	$242.10	$242.10	$242.10
Purchase #4	$207.80	7.756%	$223.917	$223.92	$223.90	$223.90
Purchase #5	$65.39	3.544%	$67.7074	$67.71	$67.70	$67.70
Purchase #6	$145.80	12.740%	$164.3749	$164.37	$164.35	$164.40
Purchase #7	$139.55	13.771%	$158.7674	$158.77	$158.75	$158.80
7 purchase totals =	$865.42		$952.4505	$952.46	$952.35	$952.50