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	$238.39	10.135%	$262.5508	$262.55	$262.55	$262.60
Purchase #2	$247.49	3.626%	$256.464	$256.46	$256.45	$256.50
Purchase #3	$35.75	7.869%	$38.5632	$38.56	$38.55	$38.60
Purchase #4	$56.51	6.323%	$60.0831	$60.08	$60.10	$60.10
Purchase #5	$236.83	11.617%	$264.3425	$264.34	$264.35	$264.30
Purchase #6	$73.87	13.541%	$83.8727	$83.87	$83.85	$83.90
Purchase #7	$131.94	5.222%	$138.8299	$138.83	$138.85	$138.80
7 purchase totals =	$1,020.78		$1,104.7062	$1,104.69	$1,104.70	$1,104.80