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	$206.42	11.805%	$230.7879	$230.79	$230.80	$230.80
Purchase #2	$102.85	6.244%	$109.272	$109.27	$109.25	$109.30
Purchase #3	$71.87	5.712%	$75.9752	$75.98	$76.00	$76.00
Purchase #4	$155.55	10.150%	$171.3383	$171.34	$171.35	$171.30
Purchase #5	$11.40	4.279%	$11.8878	$11.89	$11.90	$11.90
Purchase #6	$238.92	7.505%	$256.8509	$256.85	$256.85	$256.90
Purchase #7	$205.27	9.722%	$225.2263	$225.23	$225.25	$225.20
7 purchase totals =	$992.28		$1,081.3384	$1,081.35	$1,081.40	$1,081.40