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	$94.45	12.652%	$106.3998	$106.40	$106.40	$106.40
Purchase #2	$106.77	8.551%	$115.8999	$115.90	$115.90	$115.90
Purchase #3	$155.77	5.665%	$164.5944	$164.59	$164.60	$164.60
Purchase #4	$139.83	6.225%	$148.5344	$148.53	$148.55	$148.50
Purchase #5	$33.62	13.778%	$38.2522	$38.25	$38.25	$38.30
Purchase #6	$115.40	13.150%	$130.5751	$130.58	$130.60	$130.60
Purchase #7	$47.47	12.699%	$53.4982	$53.50	$53.50	$53.50
7 purchase totals =	$693.31		$757.7540	$757.75	$757.80	$757.80