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	$155.76	5.841%	$164.8579	$164.86	$164.85	$164.90
Purchase #2	$112.89	3.292%	$116.6063	$116.61	$116.60	$116.60
Purchase #3	$210.35	10.108%	$231.6122	$231.61	$231.60	$231.60
Purchase #4	$113.61	8.753%	$123.5543	$123.55	$123.55	$123.60
Purchase #5	$118.50	13.729%	$134.7689	$134.77	$134.75	$134.80
Purchase #6	$167.60	10.375%	$184.9885	$184.99	$185.00	$185.00
Purchase #7	$146.86	8.166%	$158.8526	$158.85	$158.85	$158.90
7 purchase totals =	$1,025.57		$1,115.2407	$1,115.24	$1,115.20	$1,115.40