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	$193.54	4.732%	$202.6983	$202.70	$202.70	$202.70
Purchase #2	$242.89	3.195%	$250.6503	$250.65	$250.65	$250.70
Purchase #3	$48.61	5.724%	$51.3924	$51.39	$51.40	$51.40
Purchase #4	$172.60	5.181%	$181.5424	$181.54	$181.55	$181.50
Purchase #5	$165.39	4.228%	$172.3827	$172.38	$172.40	$172.40
Purchase #6	$197.69	11.757%	$220.9324	$220.93	$220.95	$220.90
Purchase #7	$66.69	7.792%	$71.8865	$71.89	$71.90	$71.90
7 purchase totals =	$1,087.41		$1,151.4850	$1,151.48	$1,151.55	$1,151.50