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	$54.82	13.243%	$62.0798	$62.08	$62.10	$62.10
Purchase #2	$34.94	7.540%	$37.5745	$37.57	$37.55	$37.60
Purchase #3	$213.34	10.398%	$235.5231	$235.52	$235.50	$235.50
Purchase #4	$147.34	7.827%	$158.8723	$158.87	$158.85	$158.90
Purchase #5	$94.34	6.359%	$100.3391	$100.34	$100.35	$100.30
Purchase #6	$39.27	10.703%	$43.4731	$43.47	$43.45	$43.50
Purchase #7	$182.99	6.632%	$195.1259	$195.13	$195.15	$195.10
7 purchase totals =	$767.04		$832.9878	$832.98	$832.95	$833.00