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	$145.51	13.214%	$164.7377	$164.74	$164.75	$164.70
Purchase #2	$107.32	10.729%	$118.8344	$118.83	$118.85	$118.80
Purchase #3	$53.30	5.525%	$56.2448	$56.24	$56.25	$56.20
Purchase #4	$14.45	10.818%	$16.0132	$16.01	$16.00	$16.00
Purchase #5	$190.53	8.264%	$206.2754	$206.28	$206.30	$206.30
Purchase #6	$104.84	6.716%	$111.8811	$111.88	$111.90	$111.90
Purchase #7	$80.92	10.404%	$89.3389	$89.34	$89.35	$89.30
7 purchase totals =	$696.87		$763.3255	$763.32	$763.40	$763.20