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	$137.31	8.414%	$148.8633	$148.86	$148.85	$148.90
Purchase #2	$79.76	13.378%	$90.4303	$90.43	$90.45	$90.40
Purchase #3	$113.65	3.260%	$117.355	$117.36	$117.35	$117.40
Purchase #4	$28.73	4.203%	$29.9375	$29.94	$29.95	$29.90
Purchase #5	$226.73	13.322%	$256.935	$256.94	$256.95	$256.90
Purchase #6	$56.59	13.436%	$64.1934	$64.19	$64.20	$64.20
Purchase #7	$152.45	13.394%	$172.8692	$172.87	$172.85	$172.90
7 purchase totals =	$795.22		$880.5837	$880.59	$880.60	$880.60