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	$106.94	6.157%	$113.5243	$113.52	$113.50	$113.50
Purchase #2	$224.90	13.505%	$255.2727	$255.27	$255.25	$255.30
Purchase #3	$72.32	8.356%	$78.3631	$78.36	$78.35	$78.40
Purchase #4	$83.67	12.135%	$93.8234	$93.82	$93.80	$93.80
Purchase #5	$199.98	11.764%	$223.5056	$223.51	$223.50	$223.50
Purchase #6	$52.87	10.214%	$58.2701	$58.27	$58.25	$58.30
Purchase #7	$124.47	4.154%	$129.6405	$129.64	$129.65	$129.60
7 purchase totals =	$865.15		$952.3997	$952.39	$952.30	$952.40