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	$182.67	12.158%	$204.879	$204.88	$204.90	$204.90
Purchase #2	$90.37	7.847%	$97.4613	$97.46	$97.45	$97.50
Purchase #3	$82.62	9.241%	$90.2549	$90.25	$90.25	$90.30
Purchase #4	$84.57	11.740%	$94.4985	$94.50	$94.50	$94.50
Purchase #5	$48.97	10.268%	$53.9982	$54.00	$54.00	$54.00
Purchase #6	$125.50	5.666%	$132.6108	$132.61	$132.60	$132.60
Purchase #7	$172.73	7.490%	$185.6675	$185.67	$185.65	$185.70
7 purchase totals =	$787.43		$859.3702	$859.37	$859.35	$859.50