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	$176.34	11.874%	$197.2786	$197.28	$197.30	$197.30
Purchase #2	$99.35	12.111%	$111.3823	$111.38	$111.40	$111.40
Purchase #3	$210.39	4.820%	$220.5308	$220.53	$220.55	$220.50
Purchase #4	$49.92	5.249%	$52.5403	$52.54	$52.55	$52.50
Purchase #5	$210.58	5.199%	$221.5281	$221.53	$221.55	$221.50
Purchase #6	$144.98	12.233%	$162.7154	$162.72	$162.70	$162.70
Purchase #7	$60.76	8.344%	$65.8298	$65.83	$65.85	$65.80
7 purchase totals =	$952.32		$1,031.8053	$1,031.81	$1,031.90	$1,031.70