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	$105.45	7.257%	$113.1025	$113.10	$113.10	$113.10
Purchase #2	$92.98	13.739%	$105.7545	$105.75	$105.75	$105.80
Purchase #3	$58.54	5.215%	$61.5929	$61.59	$61.60	$61.60
Purchase #4	$227.38	12.850%	$256.5983	$256.60	$256.60	$256.60
Purchase #5	$12.88	13.216%	$14.5822	$14.58	$14.60	$14.60
Purchase #6	$241.51	9.368%	$264.1347	$264.13	$264.15	$264.10
Purchase #7	$42.41	10.435%	$46.8355	$46.84	$46.85	$46.80
7 purchase totals =	$781.15		$862.6006	$862.59	$862.65	$862.60