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	$194.46	5.706%	$205.5559	$205.56	$205.55	$205.60
Purchase #2	$218.89	9.705%	$240.1333	$240.13	$240.15	$240.10
Purchase #3	$138.85	5.482%	$146.4618	$146.46	$146.45	$146.50
Purchase #4	$187.53	6.659%	$200.0176	$200.02	$200.00	$200.00
Purchase #5	$169.48	11.161%	$188.3957	$188.40	$188.40	$188.40
Purchase #6	$169.87	10.323%	$187.4057	$187.41	$187.40	$187.40
Purchase #7	$165.50	7.863%	$178.5133	$178.51	$178.50	$178.50
7 purchase totals =	$1,244.58		$1,346.4833	$1,346.49	$1,346.45	$1,346.50