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	$242.94	4.224%	$253.2018	$253.20	$253.20	$253.20
Purchase #2	$210.51	3.300%	$217.4568	$217.46	$217.45	$217.50
Purchase #3	$60.44	11.631%	$67.4698	$67.47	$67.45	$67.50
Purchase #4	$36.49	9.851%	$40.0846	$40.08	$40.10	$40.10
Purchase #5	$176.78	10.739%	$195.7644	$195.76	$195.75	$195.80
Purchase #6	$198.40	3.443%	$205.2309	$205.23	$205.25	$205.20
Purchase #7	$95.95	4.549%	$100.3148	$100.31	$100.30	$100.30
7 purchase totals =	$1,021.51		$1,079.5231	$1,079.51	$1,079.50	$1,079.60