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	$95.29	11.160%	$105.9244	$105.92	$105.90	$105.90
Purchase #2	$141.93	11.861%	$158.7643	$158.76	$158.75	$158.80
Purchase #3	$143.58	13.333%	$162.7235	$162.72	$162.70	$162.70
Purchase #4	$230.49	12.627%	$259.594	$259.59	$259.60	$259.60
Purchase #5	$194.54	4.868%	$204.0102	$204.01	$204.00	$204.00
Purchase #6	$34.57	6.746%	$36.9021	$36.90	$36.90	$36.90
Purchase #7	$128.47	4.270%	$133.9557	$133.96	$133.95	$134.00
7 purchase totals =	$968.87		$1,061.8742	$1,061.86	$1,061.80	$1,061.90