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	$92.74	13.708%	$105.4528	$105.45	$105.45	$105.50
Purchase #2	$99.70	4.699%	$104.3849	$104.38	$104.40	$104.40
Purchase #3	$89.32	5.253%	$94.012	$94.01	$94.00	$94.00
Purchase #4	$41.75	5.799%	$44.1711	$44.17	$44.15	$44.20
Purchase #5	$40.65	12.363%	$45.6756	$45.68	$45.70	$45.70
Purchase #6	$219.80	12.651%	$247.6069	$247.61	$247.60	$247.60
Purchase #7	$153.95	8.212%	$166.5924	$166.59	$166.60	$166.60
7 purchase totals =	$737.91		$807.8957	$807.89	$807.90	$808.00