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	$62.87	10.341%	$69.3714	$69.37	$69.35	$69.40
Purchase #2	$124.86	4.553%	$130.5449	$130.54	$130.55	$130.50
Purchase #3	$130.71	6.334%	$138.9892	$138.99	$139.00	$139.00
Purchase #4	$167.37	9.199%	$182.7664	$182.77	$182.75	$182.80
Purchase #5	$30.83	3.522%	$31.9158	$31.92	$31.90	$31.90
Purchase #6	$55.33	10.575%	$61.1811	$61.18	$61.20	$61.20
Purchase #7	$88.38	13.342%	$100.1717	$100.17	$100.15	$100.20
7 purchase totals =	$660.35		$714.9405	$714.94	$714.90	$715.00