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	$64.66	12.801%	$72.9371	$72.94	$72.95	$72.90
Purchase #2	$162.26	7.663%	$174.694	$174.69	$174.70	$174.70
Purchase #3	$189.26	10.206%	$208.5759	$208.58	$208.60	$208.60
Purchase #4	$173.29	3.365%	$179.1212	$179.12	$179.10	$179.10
Purchase #5	$59.85	12.360%	$67.2475	$67.25	$67.25	$67.20
Purchase #6	$119.52	7.681%	$128.7003	$128.70	$128.70	$128.70
Purchase #7	$152.53	13.377%	$172.9339	$172.93	$172.95	$172.90
7 purchase totals =	$921.37		$1,004.2099	$1,004.21	$1,004.25	$1,004.10