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	$37.47	8.492%	$40.652	$40.65	$40.65	$40.70
Purchase #2	$66.48	8.743%	$72.2923	$72.29	$72.30	$72.30
Purchase #3	$153.65	9.826%	$168.7476	$168.75	$168.75	$168.70
Purchase #4	$154.38	4.538%	$161.3858	$161.39	$161.40	$161.40
Purchase #5	$34.62	9.212%	$37.8092	$37.81	$37.80	$37.80
Purchase #6	$250.32	5.517%	$264.1302	$264.13	$264.15	$264.10
Purchase #7	$70.80	3.429%	$73.2277	$73.23	$73.25	$73.20
7 purchase totals =	$767.72		$818.2448	$818.25	$818.30	$818.20