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	$59.74	8.164%	$64.6172	$64.62	$64.60	$64.60
Purchase #2	$85.69	5.660%	$90.5401	$90.54	$90.55	$90.50
Purchase #3	$220.77	10.196%	$243.2797	$243.28	$243.30	$243.30
Purchase #4	$182.31	13.588%	$207.0823	$207.08	$207.10	$207.10
Purchase #5	$240.96	4.830%	$252.5984	$252.60	$252.60	$252.60
Purchase #6	$32.69	13.644%	$37.1502	$37.15	$37.15	$37.20
Purchase #7	$199.36	4.338%	$208.0082	$208.01	$208.00	$208.00
7 purchase totals =	$1,021.52		$1,103.2761	$1,103.28	$1,103.30	$1,103.30