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	$82.36	10.308%	$90.8497	$90.85	$90.85	$90.80
Purchase #2	$213.31	11.680%	$238.2246	$238.22	$238.20	$238.20
Purchase #3	$41.56	13.768%	$47.282	$47.28	$47.30	$47.30
Purchase #4	$61.27	12.492%	$68.9238	$68.92	$68.90	$68.90
Purchase #5	$114.74	12.105%	$128.6293	$128.63	$128.65	$128.60
Purchase #6	$184.67	4.251%	$192.5203	$192.52	$192.50	$192.50
Purchase #7	$93.87	7.441%	$100.8549	$100.85	$100.85	$100.90
7 purchase totals =	$791.78		$867.2846	$867.27	$867.25	$867.20