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	$62.42	11.401%	$69.5365	$69.54	$69.55	$69.50
Purchase #2	$152.55	10.562%	$168.6623	$168.66	$168.65	$168.70
Purchase #3	$239.67	6.573%	$255.4235	$255.42	$255.40	$255.40
Purchase #4	$30.51	7.368%	$32.758	$32.76	$32.75	$32.80
Purchase #5	$67.56	6.607%	$72.0237	$72.02	$72.00	$72.00
Purchase #6	$77.37	12.861%	$87.3206	$87.32	$87.30	$87.30
Purchase #7	$138.27	5.654%	$146.0878	$146.09	$146.10	$146.10
7 purchase totals =	$768.35		$831.8124	$831.81	$831.75	$831.80