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	$119.72	6.459%	$127.4527	$127.45	$127.45	$127.50
Purchase #2	$91.50	3.401%	$94.6119	$94.61	$94.60	$94.60
Purchase #3	$35.62	6.167%	$37.8167	$37.82	$37.80	$37.80
Purchase #4	$129.81	5.478%	$136.921	$136.92	$136.90	$136.90
Purchase #5	$91.50	10.216%	$100.8476	$100.85	$100.85	$100.80
Purchase #6	$59.69	7.873%	$64.3894	$64.39	$64.40	$64.40
Purchase #7	$61.68	8.549%	$66.953	$66.95	$66.95	$67.00
7 purchase totals =	$589.52		$628.9923	$628.99	$628.95	$629.00