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	$202.50	10.401%	$223.562	$223.56	$223.55	$223.60
Purchase #2	$83.77	8.315%	$90.7355	$90.74	$90.75	$90.70
Purchase #3	$48.89	3.874%	$50.784	$50.78	$50.80	$50.80
Purchase #4	$193.52	11.395%	$215.5716	$215.57	$215.55	$215.60
Purchase #5	$116.88	3.146%	$120.557	$120.56	$120.55	$120.60
Purchase #6	$142.70	9.491%	$156.2437	$156.24	$156.25	$156.20
Purchase #7	$66.90	7.659%	$72.0239	$72.02	$72.00	$72.00
7 purchase totals =	$855.16		$929.4777	$929.47	$929.45	$929.50