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	$98.27	5.454%	$103.6296	$103.63	$103.65	$103.60
Purchase #2	$228.32	10.120%	$251.426	$251.43	$251.45	$251.40
Purchase #3	$21.61	4.870%	$22.6624	$22.66	$22.65	$22.70
Purchase #4	$48.80	7.113%	$52.2711	$52.27	$52.25	$52.30
Purchase #5	$65.67	5.760%	$69.4526	$69.45	$69.45	$69.50
Purchase #6	$219.75	4.381%	$229.3772	$229.38	$229.40	$229.40
Purchase #7	$43.56	5.127%	$45.7933	$45.79	$45.80	$45.80
7 purchase totals =	$725.98		$774.6122	$774.61	$774.65	$774.70