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	$180.77	8.757%	$196.6	$196.60	$196.60	$196.60
Purchase #2	$60.89	11.579%	$67.9405	$67.94	$67.95	$67.90
Purchase #3	$242.81	13.103%	$274.6254	$274.63	$274.65	$274.60
Purchase #4	$149.38	5.454%	$157.5272	$157.53	$157.55	$157.50
Purchase #5	$38.82	8.525%	$42.1294	$42.13	$42.15	$42.10
Purchase #6	$124.33	8.864%	$135.3506	$135.35	$135.35	$135.40
Purchase #7	$124.85	5.709%	$131.9777	$131.98	$132.00	$132.00
7 purchase totals =	$921.85		$1,006.1508	$1,006.16	$1,006.25	$1,006.10