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	$210.72	5.391%	$222.0799	$222.08	$222.10	$222.10
Purchase #2	$192.84	3.440%	$199.4737	$199.47	$199.45	$199.50
Purchase #3	$37.89	11.832%	$42.3731	$42.37	$42.35	$42.40
Purchase #4	$144.32	6.687%	$153.9707	$153.97	$153.95	$154.00
Purchase #5	$90.84	9.351%	$99.3344	$99.33	$99.35	$99.30
Purchase #6	$5.82	8.567%	$6.3186	$6.32	$6.30	$6.30
Purchase #7	$6.81	8.385%	$7.381	$7.38	$7.40	$7.40
7 purchase totals =	$689.24		$730.9314	$730.92	$730.90	$731.00