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	$154.84	13.120%	$175.155	$175.16	$175.15	$175.20
Purchase #2	$88.52	4.243%	$92.2759	$92.28	$92.30	$92.30
Purchase #3	$234.87	11.269%	$261.3375	$261.34	$261.35	$261.30
Purchase #4	$226.84	3.529%	$234.8452	$234.85	$234.85	$234.80
Purchase #5	$81.29	10.722%	$90.0059	$90.01	$90.00	$90.00
Purchase #6	$64.97	11.798%	$72.6352	$72.64	$72.65	$72.60
Purchase #7	$53.73	5.236%	$56.5433	$56.54	$56.55	$56.50
7 purchase totals =	$905.06		$982.7980	$982.82	$982.85	$982.70