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	$56.31	11.271%	$62.6567	$62.66	$62.65	$62.70
Purchase #2	$166.61	13.488%	$189.0824	$189.08	$189.10	$189.10
Purchase #3	$152.37	5.301%	$160.4471	$160.45	$160.45	$160.40
Purchase #4	$224.77	13.786%	$255.7568	$255.76	$255.75	$255.80
Purchase #5	$184.83	7.426%	$198.5555	$198.56	$198.55	$198.60
Purchase #6	$77.73	9.284%	$84.9465	$84.95	$84.95	$84.90
Purchase #7	$164.75	9.535%	$180.4589	$180.46	$180.45	$180.50
7 purchase totals =	$1,027.37		$1,131.9039	$1,131.92	$1,131.90	$1,132.00