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	$59.77	13.515%	$67.8479	$67.85	$67.85	$67.80
Purchase #2	$14.50	12.545%	$16.319	$16.32	$16.30	$16.30
Purchase #3	$141.65	7.874%	$152.8035	$152.80	$152.80	$152.80
Purchase #4	$148.64	13.243%	$168.3244	$168.32	$168.30	$168.30
Purchase #5	$233.42	9.253%	$255.0184	$255.02	$255.00	$255.00
Purchase #6	$203.25	3.455%	$210.2723	$210.27	$210.25	$210.30
Purchase #7	$34.75	8.421%	$37.6763	$37.68	$37.70	$37.70
7 purchase totals =	$835.98		$908.2618	$908.26	$908.20	$908.20