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	$71.36	9.437%	$78.0942	$78.09	$78.10	$78.10
Purchase #2	$150.87	7.295%	$161.876	$161.88	$161.90	$161.90
Purchase #3	$138.82	3.171%	$143.222	$143.22	$143.20	$143.20
Purchase #4	$96.63	3.733%	$100.2372	$100.24	$100.25	$100.20
Purchase #5	$234.73	11.245%	$261.1254	$261.13	$261.15	$261.10
Purchase #6	$133.87	10.832%	$148.3708	$148.37	$148.35	$148.40
Purchase #7	$196.32	5.411%	$206.9429	$206.94	$206.95	$206.90
7 purchase totals =	$1,022.60		$1,099.8685	$1,099.87	$1,099.90	$1,099.80