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	$51.66	12.331%	$58.0302	$58.03	$58.05	$58.00
Purchase #2	$157.78	11.293%	$175.5981	$175.60	$175.60	$175.60
Purchase #3	$35.35	13.418%	$40.0933	$40.09	$40.10	$40.10
Purchase #4	$167.94	10.247%	$185.1488	$185.15	$185.15	$185.10
Purchase #5	$77.92	13.323%	$88.3013	$88.30	$88.30	$88.30
Purchase #6	$56.32	13.646%	$64.0054	$64.01	$64.00	$64.00
Purchase #7	$98.39	13.440%	$111.6136	$111.61	$111.60	$111.60
7 purchase totals =	$645.36		$722.7907	$722.79	$722.80	$722.70