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	$179.37	9.450%	$196.3205	$196.32	$196.30	$196.30
Purchase #2	$223.45	13.650%	$253.9509	$253.95	$253.95	$254.00
Purchase #3	$144.55	12.387%	$162.4554	$162.46	$162.45	$162.50
Purchase #4	$152.58	4.176%	$158.9517	$158.95	$158.95	$159.00
Purchase #5	$27.47	3.236%	$28.3589	$28.36	$28.35	$28.40
Purchase #6	$178.77	12.208%	$200.5942	$200.59	$200.60	$200.60
Purchase #7	$38.63	5.614%	$40.7987	$40.80	$40.80	$40.80
7 purchase totals =	$944.82		$1,041.4303	$1,041.43	$1,041.40	$1,041.60