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	$48.41	13.688%	$55.0364	$55.04	$55.05	$55.00
Purchase #2	$217.48	9.163%	$237.4077	$237.41	$237.40	$237.40
Purchase #3	$249.94	9.193%	$272.917	$272.92	$272.90	$272.90
Purchase #4	$33.77	10.587%	$37.3452	$37.35	$37.35	$37.30
Purchase #5	$249.78	10.105%	$275.0203	$275.02	$275.00	$275.00
Purchase #6	$55.63	12.333%	$62.4908	$62.49	$62.50	$62.50
Purchase #7	$162.25	4.707%	$169.8871	$169.89	$169.90	$169.90
7 purchase totals =	$1,017.26		$1,110.1045	$1,110.12	$1,110.10	$1,110.00