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	$69.83	3.341%	$72.163	$72.16	$72.15	$72.20
Purchase #2	$220.46	8.104%	$238.3261	$238.33	$238.35	$238.30
Purchase #3	$78.75	6.244%	$83.6672	$83.67	$83.65	$83.70
Purchase #4	$179.89	8.124%	$194.5043	$194.50	$194.50	$194.50
Purchase #5	$176.38	6.312%	$187.5131	$187.51	$187.50	$187.50
Purchase #6	$134.80	13.440%	$152.9171	$152.92	$152.90	$152.90
Purchase #7	$65.80	13.366%	$74.5948	$74.59	$74.60	$74.60
7 purchase totals =	$925.91		$1,003.6856	$1,003.68	$1,003.65	$1,003.70