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	$76.85	3.487%	$79.5298	$79.53	$79.55	$79.50
Purchase #2	$134.66	13.682%	$153.0842	$153.08	$153.10	$153.10
Purchase #3	$9.67	13.222%	$10.9486	$10.95	$10.95	$10.90
Purchase #4	$137.35	12.826%	$154.9665	$154.97	$154.95	$155.00
Purchase #5	$78.96	4.455%	$82.4777	$82.48	$82.50	$82.50
Purchase #6	$55.28	10.852%	$61.279	$61.28	$61.30	$61.30
Purchase #7	$174.84	3.628%	$181.1832	$181.18	$181.20	$181.20
7 purchase totals =	$667.61		$723.4690	$723.47	$723.55	$723.50