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	$204.92	9.110%	$223.5882	$223.59	$223.60	$223.60
Purchase #2	$17.86	5.304%	$18.8073	$18.81	$18.80	$18.80
Purchase #3	$179.89	4.797%	$188.5193	$188.52	$188.50	$188.50
Purchase #4	$227.40	11.734%	$254.0831	$254.08	$254.10	$254.10
Purchase #5	$139.84	5.247%	$147.1774	$147.18	$147.20	$147.20
Purchase #6	$41.44	10.214%	$45.6727	$45.67	$45.65	$45.70
Purchase #7	$131.26	10.806%	$145.444	$145.44	$145.45	$145.40
7 purchase totals =	$942.61		$1,023.2920	$1,023.29	$1,023.30	$1,023.30