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	$210.35	6.794%	$224.6412	$224.64	$224.65	$224.60
Purchase #2	$184.85	9.686%	$202.7546	$202.75	$202.75	$202.80
Purchase #3	$150.64	10.565%	$166.5551	$166.56	$166.55	$166.60
Purchase #4	$20.76	5.316%	$21.8636	$21.86	$21.85	$21.90
Purchase #5	$77.76	6.418%	$82.7506	$82.75	$82.75	$82.80
Purchase #6	$173.61	7.302%	$186.287	$186.29	$186.30	$186.30
Purchase #7	$205.75	13.497%	$233.5201	$233.52	$233.50	$233.50
7 purchase totals =	$1,023.72		$1,118.3722	$1,118.37	$1,118.35	$1,118.50