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	$65.54	11.770%	$73.2541	$73.25	$73.25	$73.30
Purchase #2	$84.50	6.859%	$90.2959	$90.30	$90.30	$90.30
Purchase #3	$115.64	4.838%	$121.2347	$121.23	$121.25	$121.20
Purchase #4	$76.88	12.697%	$86.6415	$86.64	$86.65	$86.60
Purchase #5	$214.63	3.606%	$222.3696	$222.37	$222.35	$222.40
Purchase #6	$222.75	13.772%	$253.4271	$253.43	$253.45	$253.40
Purchase #7	$72.25	13.740%	$82.1772	$82.18	$82.20	$82.20
7 purchase totals =	$852.19		$929.4001	$929.40	$929.45	$929.40