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	$111.54	13.110%	$126.1629	$126.16	$126.15	$126.20
Purchase #2	$35.44	10.446%	$39.1421	$39.14	$39.15	$39.10
Purchase #3	$111.51	13.859%	$126.9642	$126.96	$126.95	$127.00
Purchase #4	$34.27	12.226%	$38.4599	$38.46	$38.45	$38.50
Purchase #5	$201.41	11.634%	$224.842	$224.84	$224.85	$224.80
Purchase #6	$200.86	4.601%	$210.1016	$210.10	$210.10	$210.10
Purchase #7	$40.97	5.517%	$43.2303	$43.23	$43.25	$43.20
7 purchase totals =	$736.00		$808.9030	$808.89	$808.90	$808.90