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	$130.98	8.827%	$142.5416	$142.54	$142.55	$142.50
Purchase #2	$104.66	3.312%	$108.1263	$108.13	$108.15	$108.10
Purchase #3	$24.37	12.732%	$27.4728	$27.47	$27.45	$27.50
Purchase #4	$175.59	8.487%	$190.4923	$190.49	$190.50	$190.50
Purchase #5	$201.33	11.674%	$224.8333	$224.83	$224.85	$224.80
Purchase #6	$133.35	8.657%	$144.8941	$144.89	$144.90	$144.90
Purchase #7	$109.96	13.245%	$124.5242	$124.52	$124.50	$124.50
7 purchase totals =	$880.24		$962.8846	$962.87	$962.90	$962.80