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	$24.60	6.162%	$26.1159	$26.12	$26.10	$26.10
Purchase #2	$153.75	11.183%	$170.9439	$170.94	$170.95	$170.90
Purchase #3	$177.82	9.443%	$194.6115	$194.61	$194.60	$194.60
Purchase #4	$164.84	8.709%	$179.1959	$179.20	$179.20	$179.20
Purchase #5	$170.66	11.520%	$190.32	$190.32	$190.30	$190.30
Purchase #6	$170.27	10.410%	$187.9951	$188.00	$188.00	$188.00
Purchase #7	$57.39	4.260%	$59.8348	$59.83	$59.85	$59.80
7 purchase totals =	$919.33		$1,009.0171	$1,009.02	$1,009.00	$1,008.90