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	$202.54	3.108%	$208.8349	$208.83	$208.85	$208.80
Purchase #2	$137.35	13.478%	$155.862	$155.86	$155.85	$155.90
Purchase #3	$233.56	3.584%	$241.9308	$241.93	$241.95	$241.90
Purchase #4	$154.40	6.674%	$164.7047	$164.70	$164.70	$164.70
Purchase #5	$62.55	3.515%	$64.7486	$64.75	$64.75	$64.70
Purchase #6	$56.42	3.846%	$58.5899	$58.59	$58.60	$58.60
Purchase #7	$191.79	7.286%	$205.7638	$205.76	$205.75	$205.80
7 purchase totals =	$1,038.61		$1,100.4347	$1,100.42	$1,100.45	$1,100.40