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	$179.27	10.766%	$198.5702	$198.57	$198.55	$198.60
Purchase #2	$177.81	7.136%	$190.4985	$190.50	$190.50	$190.50
Purchase #3	$104.56	4.874%	$109.6563	$109.66	$109.65	$109.70
Purchase #4	$118.86	5.395%	$125.2725	$125.27	$125.25	$125.30
Purchase #5	$102.28	9.145%	$111.6335	$111.63	$111.65	$111.60
Purchase #6	$22.65	10.608%	$25.0527	$25.05	$25.05	$25.10
Purchase #7	$163.48	3.138%	$168.61	$168.61	$168.60	$168.60
7 purchase totals =	$868.91		$929.2937	$929.29	$929.25	$929.40