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	$66.92	6.749%	$71.4364	$71.44	$71.45	$71.40
Purchase #2	$40.32	8.461%	$43.7315	$43.73	$43.75	$43.70
Purchase #3	$34.59	9.274%	$37.7979	$37.80	$37.80	$37.80
Purchase #4	$150.76	10.697%	$166.8868	$166.89	$166.90	$166.90
Purchase #5	$192.71	11.377%	$214.6346	$214.63	$214.65	$214.60
Purchase #6	$46.35	12.641%	$52.2091	$52.21	$52.20	$52.20
Purchase #7	$133.48	13.850%	$151.967	$151.97	$151.95	$152.00
7 purchase totals =	$665.13		$738.6633	$738.67	$738.70	$738.60