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	$215.53	5.366%	$227.0953	$227.10	$227.10	$227.10
Purchase #2	$75.56	4.195%	$78.7297	$78.73	$78.75	$78.70
Purchase #3	$174.25	12.805%	$196.5627	$196.56	$196.55	$196.60
Purchase #4	$142.50	3.104%	$146.9232	$146.92	$146.90	$146.90
Purchase #5	$72.32	8.761%	$78.656	$78.66	$78.65	$78.70
Purchase #6	$201.92	13.546%	$229.2721	$229.27	$229.25	$229.30
Purchase #7	$36.73	8.162%	$39.7279	$39.73	$39.75	$39.70
7 purchase totals =	$918.81		$996.9669	$996.97	$996.95	$997.00