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	$46.59	11.608%	$51.9982	$52.00	$52.00	$52.00
Purchase #2	$118.43	10.849%	$131.2785	$131.28	$131.30	$131.30
Purchase #3	$160.34	3.615%	$166.1363	$166.14	$166.15	$166.10
Purchase #4	$146.91	4.110%	$152.948	$152.95	$152.95	$152.90
Purchase #5	$177.91	7.492%	$191.239	$191.24	$191.25	$191.20
Purchase #6	$168.98	12.593%	$190.2597	$190.26	$190.25	$190.30
Purchase #7	$204.73	9.225%	$223.6163	$223.62	$223.60	$223.60
7 purchase totals =	$1,023.89		$1,107.4760	$1,107.49	$1,107.50	$1,107.40