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	$196.59	12.703%	$221.5628	$221.56	$221.55	$221.60
Purchase #2	$118.78	11.782%	$132.7747	$132.77	$132.75	$132.80
Purchase #3	$184.82	12.307%	$207.5658	$207.57	$207.55	$207.60
Purchase #4	$129.39	12.691%	$145.8109	$145.81	$145.80	$145.80
Purchase #5	$130.88	13.475%	$148.5161	$148.52	$148.50	$148.50
Purchase #6	$181.78	8.124%	$196.5478	$196.55	$196.55	$196.50
Purchase #7	$206.43	8.383%	$223.735	$223.74	$223.75	$223.70
7 purchase totals =	$1,148.67		$1,276.5131	$1,276.52	$1,276.45	$1,276.50