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	$134.95	12.548%	$151.8835	$151.88	$151.90	$151.90
Purchase #2	$51.36	3.649%	$53.2341	$53.23	$53.25	$53.20
Purchase #3	$81.60	4.735%	$85.4638	$85.46	$85.45	$85.50
Purchase #4	$107.67	7.312%	$115.5428	$115.54	$115.55	$115.50
Purchase #5	$127.85	7.182%	$137.0322	$137.03	$137.05	$137.00
Purchase #6	$137.90	13.210%	$156.1166	$156.12	$156.10	$156.10
Purchase #7	$245.90	7.771%	$265.0089	$265.01	$265.00	$265.00
7 purchase totals =	$887.23		$964.2819	$964.27	$964.30	$964.20