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	$80.64	8.339%	$87.3646	$87.36	$87.35	$87.40
Purchase #2	$28.27	3.759%	$29.3327	$29.33	$29.35	$29.30
Purchase #3	$176.55	11.348%	$196.5849	$196.58	$196.60	$196.60
Purchase #4	$54.32	13.293%	$61.5408	$61.54	$61.55	$61.50
Purchase #5	$16.27	10.786%	$18.0249	$18.02	$18.00	$18.00
Purchase #6	$86.38	8.128%	$93.401	$93.40	$93.40	$93.40
Purchase #7	$24.40	6.163%	$25.9038	$25.90	$25.90	$25.90
7 purchase totals =	$466.83		$512.1527	$512.13	$512.15	$512.10