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	$216.80	3.480%	$224.3446	$224.34	$224.35	$224.30
Purchase #2	$16.87	12.329%	$18.9499	$18.95	$18.95	$18.90
Purchase #3	$220.28	8.193%	$238.3275	$238.33	$238.35	$238.30
Purchase #4	$132.51	8.686%	$144.0198	$144.02	$144.00	$144.00
Purchase #5	$89.34	9.196%	$97.5557	$97.56	$97.55	$97.60
Purchase #6	$92.61	13.333%	$104.9577	$104.96	$104.95	$105.00
Purchase #7	$93.67	7.307%	$100.5145	$100.51	$100.50	$100.50
7 purchase totals =	$862.08		$928.6697	$928.67	$928.65	$928.60