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	$49.47	13.234%	$56.0169	$56.02	$56.00	$56.00
Purchase #2	$207.64	6.566%	$221.2736	$221.27	$221.25	$221.30
Purchase #3	$223.88	6.450%	$238.3203	$238.32	$238.30	$238.30
Purchase #4	$90.32	11.737%	$100.9209	$100.92	$100.90	$100.90
Purchase #5	$145.38	3.620%	$150.6428	$150.64	$150.65	$150.60
Purchase #6	$191.89	10.304%	$211.6623	$211.66	$211.65	$211.70
Purchase #7	$49.48	6.533%	$52.7125	$52.71	$52.70	$52.70
7 purchase totals =	$958.06		$1,031.5493	$1,031.54	$1,031.45	$1,031.50