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	$92.91	7.511%	$99.8885	$99.89	$99.90	$99.90
Purchase #2	$238.50	7.184%	$255.6338	$255.63	$255.65	$255.60
Purchase #3	$159.90	10.390%	$176.5136	$176.51	$176.50	$176.50
Purchase #4	$144.44	11.512%	$161.0679	$161.07	$161.05	$161.10
Purchase #5	$71.50	10.186%	$78.783	$78.78	$78.80	$78.80
Purchase #6	$231.82	3.307%	$239.4863	$239.49	$239.50	$239.50
Purchase #7	$192.56	11.163%	$214.0555	$214.06	$214.05	$214.10
7 purchase totals =	$1,131.63		$1,225.4286	$1,225.43	$1,225.45	$1,225.50