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	$215.63	8.382%	$233.7041	$233.70	$233.70	$233.70
Purchase #2	$112.60	3.173%	$116.1728	$116.17	$116.15	$116.20
Purchase #3	$104.77	6.485%	$111.5643	$111.56	$111.55	$111.60
Purchase #4	$36.93	12.760%	$41.6423	$41.64	$41.65	$41.60
Purchase #5	$162.71	13.139%	$184.0885	$184.09	$184.10	$184.10
Purchase #6	$221.86	5.436%	$233.9203	$233.92	$233.90	$233.90
Purchase #7	$63.94	8.601%	$69.4395	$69.44	$69.45	$69.40
7 purchase totals =	$918.44		$990.5318	$990.52	$990.50	$990.50