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	$111.75	12.323%	$125.521	$125.52	$125.50	$125.50
Purchase #2	$33.87	7.644%	$36.459	$36.46	$36.45	$36.50
Purchase #3	$58.79	4.863%	$61.649	$61.65	$61.65	$61.60
Purchase #4	$98.37	10.463%	$108.6625	$108.66	$108.65	$108.70
Purchase #5	$188.52	6.798%	$201.3356	$201.34	$201.35	$201.30
Purchase #6	$242.88	5.557%	$256.3768	$256.38	$256.40	$256.40
Purchase #7	$168.32	11.792%	$188.1683	$188.17	$188.15	$188.20
7 purchase totals =	$902.50		$978.1722	$978.18	$978.15	$978.20