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	$48.71	6.664%	$51.956	$51.96	$51.95	$52.00
Purchase #2	$32.81	8.312%	$35.5372	$35.54	$35.55	$35.50
Purchase #3	$62.46	4.683%	$65.385	$65.39	$65.40	$65.40
Purchase #4	$187.37	4.400%	$195.6143	$195.61	$195.60	$195.60
Purchase #5	$53.66	9.710%	$58.8704	$58.87	$58.85	$58.90
Purchase #6	$102.66	11.552%	$114.5193	$114.52	$114.50	$114.50
Purchase #7	$119.72	6.641%	$127.6706	$127.67	$127.65	$127.70
7 purchase totals =	$607.39		$649.5528	$649.56	$649.50	$649.60