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	$243.94	5.123%	$256.437	$256.44	$256.45	$256.40
Purchase #2	$88.51	7.287%	$94.9597	$94.96	$94.95	$95.00
Purchase #3	$250.88	5.823%	$265.4887	$265.49	$265.50	$265.50
Purchase #4	$152.60	10.252%	$168.2446	$168.24	$168.25	$168.20
Purchase #5	$12.69	9.805%	$13.9343	$13.93	$13.95	$13.90
Purchase #6	$228.32	13.126%	$258.2893	$258.29	$258.30	$258.30
Purchase #7	$175.78	7.454%	$188.8826	$188.88	$188.90	$188.90
7 purchase totals =	$1,152.72		$1,246.2362	$1,246.23	$1,246.30	$1,246.20