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	$9.54	13.567%	$10.8343	$10.83	$10.85	$10.80
Purchase #2	$157.98	10.233%	$174.1461	$174.15	$174.15	$174.10
Purchase #3	$182.68	6.528%	$194.6054	$194.61	$194.60	$194.60
Purchase #4	$86.89	5.172%	$91.384	$91.38	$91.40	$91.40
Purchase #5	$54.95	5.432%	$57.9349	$57.93	$57.95	$57.90
Purchase #6	$231.30	4.395%	$241.4656	$241.47	$241.45	$241.50
Purchase #7	$239.62	3.661%	$248.3925	$248.39	$248.40	$248.40
7 purchase totals =	$962.96		$1,018.7628	$1,018.76	$1,018.80	$1,018.70