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	$43.72	11.851%	$48.9013	$48.90	$48.90	$48.90
Purchase #2	$32.49	9.258%	$35.4979	$35.50	$35.50	$35.50
Purchase #3	$192.99	12.726%	$217.5499	$217.55	$217.55	$217.50
Purchase #4	$6.99	4.415%	$7.2986	$7.30	$7.30	$7.30
Purchase #5	$19.80	9.549%	$21.6907	$21.69	$21.70	$21.70
Purchase #6	$151.90	10.216%	$167.4181	$167.42	$167.40	$167.40
Purchase #7	$43.83	6.323%	$46.6014	$46.60	$46.60	$46.60
7 purchase totals =	$491.72		$544.9579	$544.96	$544.95	$544.90