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	$44.77	8.529%	$48.5884	$48.59	$48.60	$48.60
Purchase #2	$6.88	11.332%	$7.6596	$7.66	$7.65	$7.70
Purchase #3	$63.68	10.110%	$70.118	$70.12	$70.10	$70.10
Purchase #4	$86.63	7.369%	$93.0138	$93.01	$93.00	$93.00
Purchase #5	$113.80	8.144%	$123.0679	$123.07	$123.05	$123.10
Purchase #6	$92.76	8.193%	$100.3598	$100.36	$100.35	$100.40
Purchase #7	$83.35	7.757%	$89.8155	$89.82	$89.80	$89.80
7 purchase totals =	$491.87		$532.6230	$532.63	$532.55	$532.70