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	$108.65	7.364%	$116.651	$116.65	$116.65	$116.70
Purchase #2	$33.26	10.304%	$36.6871	$36.69	$36.70	$36.70
Purchase #3	$55.59	3.192%	$57.3644	$57.36	$57.35	$57.40
Purchase #4	$247.52	7.397%	$265.8291	$265.83	$265.85	$265.80
Purchase #5	$5.81	11.116%	$6.4558	$6.46	$6.45	$6.50
Purchase #6	$153.89	7.438%	$165.3363	$165.34	$165.35	$165.30
Purchase #7	$127.38	3.485%	$131.8192	$131.82	$131.80	$131.80
7 purchase totals =	$732.10		$780.1429	$780.15	$780.15	$780.20