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	$43.32	5.742%	$45.8074	$45.81	$45.80	$45.80
Purchase #2	$155.48	5.633%	$164.2382	$164.24	$164.25	$164.20
Purchase #3	$33.54	4.632%	$35.0936	$35.09	$35.10	$35.10
Purchase #4	$6.91	10.784%	$7.6552	$7.66	$7.65	$7.70
Purchase #5	$52.53	13.361%	$59.5485	$59.55	$59.55	$59.50
Purchase #6	$11.51	8.490%	$12.4872	$12.49	$12.50	$12.50
Purchase #7	$71.66	13.174%	$81.1005	$81.10	$81.10	$81.10
7 purchase totals =	$374.95		$405.9306	$405.94	$405.95	$405.90