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	$55.28	10.481%	$61.0739	$61.07	$61.05	$61.10
Purchase #2	$54.55	11.841%	$61.0093	$61.01	$61.00	$61.00
Purchase #3	$205.87	5.790%	$217.7899	$217.79	$217.80	$217.80
Purchase #4	$196.67	6.180%	$208.8242	$208.82	$208.80	$208.80
Purchase #5	$18.34	13.505%	$20.8168	$20.82	$20.80	$20.80
Purchase #6	$217.91	12.392%	$244.9134	$244.91	$244.90	$244.90
Purchase #7	$103.52	9.656%	$113.5159	$113.52	$113.50	$113.50
7 purchase totals =	$852.14		$927.9434	$927.94	$927.85	$927.90