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	$63.66	5.381%	$67.0855	$67.09	$67.10	$67.10
Purchase #2	$95.41	3.519%	$98.7675	$98.77	$98.75	$98.80
Purchase #3	$122.55	8.150%	$132.5378	$132.54	$132.55	$132.50
Purchase #4	$92.66	7.808%	$99.8949	$99.89	$99.90	$99.90
Purchase #5	$21.31	4.559%	$22.2815	$22.28	$22.30	$22.30
Purchase #6	$214.86	8.711%	$233.5765	$233.58	$233.60	$233.60
Purchase #7	$64.95	9.589%	$71.1781	$71.18	$71.20	$71.20
7 purchase totals =	$675.40		$725.3218	$725.33	$725.40	$725.40