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	$214.56	8.368%	$232.5144	$232.51	$232.50	$232.50
Purchase #2	$135.87	9.478%	$148.7478	$148.75	$148.75	$148.70
Purchase #3	$172.87	3.611%	$179.1123	$179.11	$179.10	$179.10
Purchase #4	$37.36	7.598%	$40.1986	$40.20	$40.20	$40.20
Purchase #5	$142.83	12.639%	$160.8823	$160.88	$160.90	$160.90
Purchase #6	$98.54	13.542%	$111.8843	$111.88	$111.90	$111.90
Purchase #7	$198.82	12.848%	$224.3644	$224.36	$224.35	$224.40
7 purchase totals =	$1,000.85		$1,097.7041	$1,097.69	$1,097.70	$1,097.70