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	$92.76	10.420%	$102.4256	$102.43	$102.45	$102.40
Purchase #2	$37.90	13.756%	$43.1135	$43.11	$43.10	$43.10
Purchase #3	$42.59	9.821%	$46.7728	$46.77	$46.75	$46.80
Purchase #4	$165.72	12.693%	$186.7548	$186.75	$186.75	$186.80
Purchase #5	$50.45	6.828%	$53.8947	$53.89	$53.90	$53.90
Purchase #6	$248.76	3.666%	$257.8795	$257.88	$257.90	$257.90
Purchase #7	$217.50	9.705%	$238.6084	$238.61	$238.60	$238.60
7 purchase totals =	$855.68		$929.4493	$929.44	$929.45	$929.50