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	$62.56	4.842%	$65.5892	$65.59	$65.60	$65.60
Purchase #2	$174.33	10.408%	$192.4743	$192.47	$192.45	$192.50
Purchase #3	$216.94	10.252%	$239.1807	$239.18	$239.20	$239.20
Purchase #4	$227.67	10.645%	$251.9055	$251.91	$251.90	$251.90
Purchase #5	$154.84	6.222%	$164.4741	$164.47	$164.45	$164.50
Purchase #6	$60.82	3.455%	$62.9213	$62.92	$62.90	$62.90
Purchase #7	$170.38	3.277%	$175.9634	$175.96	$175.95	$176.00
7 purchase totals =	$1,067.54		$1,152.5085	$1,152.50	$1,152.45	$1,152.60