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	$9.72	12.787%	$10.9629	$10.96	$10.95	$11.00
Purchase #2	$144.29	13.404%	$163.6306	$163.63	$163.65	$163.60
Purchase #3	$127.66	3.256%	$131.8166	$131.82	$131.80	$131.80
Purchase #4	$180.43	6.367%	$191.918	$191.92	$191.90	$191.90
Purchase #5	$225.61	13.401%	$255.844	$255.84	$255.85	$255.80
Purchase #6	$158.30	8.646%	$171.9866	$171.99	$172.00	$172.00
Purchase #7	$25.43	11.737%	$28.4147	$28.41	$28.40	$28.40
7 purchase totals =	$871.44		$954.5734	$954.57	$954.55	$954.50