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	$42.93	6.727%	$45.8179	$45.82	$45.80	$45.80
Purchase #2	$81.98	5.685%	$86.6406	$86.64	$86.65	$86.60
Purchase #3	$231.31	7.774%	$249.292	$249.29	$249.30	$249.30
Purchase #4	$157.25	7.106%	$168.4242	$168.42	$168.40	$168.40
Purchase #5	$183.59	8.791%	$199.7294	$199.73	$199.75	$199.70
Purchase #6	$244.59	12.286%	$274.6403	$274.64	$274.65	$274.60
Purchase #7	$176.60	8.248%	$191.166	$191.17	$191.15	$191.20
7 purchase totals =	$1,118.25		$1,215.7104	$1,215.71	$1,215.70	$1,215.60