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	$198.34	8.237%	$214.6773	$214.68	$214.70	$214.70
Purchase #2	$35.83	5.789%	$37.9042	$37.90	$37.90	$37.90
Purchase #3	$66.79	9.154%	$72.904	$72.90	$72.90	$72.90
Purchase #4	$42.90	8.717%	$46.6396	$46.64	$46.65	$46.60
Purchase #5	$14.79	6.758%	$15.7895	$15.79	$15.80	$15.80
Purchase #6	$64.30	5.464%	$67.8134	$67.81	$67.80	$67.80
Purchase #7	$206.84	4.858%	$216.8883	$216.89	$216.90	$216.90
7 purchase totals =	$629.79		$672.6163	$672.61	$672.65	$672.60