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	$43.61	9.777%	$47.8737	$47.87	$47.85	$47.90
Purchase #2	$153.25	6.132%	$162.6473	$162.65	$162.65	$162.60
Purchase #3	$165.36	4.276%	$172.4308	$172.43	$172.45	$172.40
Purchase #4	$250.61	11.278%	$278.8738	$278.87	$278.85	$278.90
Purchase #5	$151.29	9.659%	$165.9031	$165.90	$165.90	$165.90
Purchase #6	$222.47	12.513%	$250.3077	$250.31	$250.30	$250.30
Purchase #7	$181.26	7.634%	$195.0974	$195.10	$195.10	$195.10
7 purchase totals =	$1,167.85		$1,273.1338	$1,273.13	$1,273.10	$1,273.10