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	$66.76	8.452%	$72.4026	$72.40	$72.40	$72.40
Purchase #2	$165.63	7.708%	$178.3968	$178.40	$178.40	$178.40
Purchase #3	$225.95	6.842%	$241.4095	$241.41	$241.40	$241.40
Purchase #4	$75.94	3.402%	$78.5235	$78.52	$78.50	$78.50
Purchase #5	$122.28	3.549%	$126.6197	$126.62	$126.60	$126.60
Purchase #6	$234.84	10.803%	$260.2098	$260.21	$260.20	$260.20
Purchase #7	$109.59	12.471%	$123.257	$123.26	$123.25	$123.30
7 purchase totals =	$1,000.99		$1,080.8189	$1,080.82	$1,080.75	$1,080.80