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	$225.27	6.223%	$239.2886	$239.29	$239.30	$239.30
Purchase #2	$94.54	7.571%	$101.6976	$101.70	$101.70	$101.70
Purchase #3	$34.27	4.704%	$35.8821	$35.88	$35.90	$35.90
Purchase #4	$134.39	7.573%	$144.5674	$144.57	$144.55	$144.60
Purchase #5	$35.39	12.138%	$39.6856	$39.69	$39.70	$39.70
Purchase #6	$114.51	3.808%	$118.8705	$118.87	$118.85	$118.90
Purchase #7	$52.94	3.665%	$54.8803	$54.88	$54.90	$54.90
7 purchase totals =	$691.31		$734.8721	$734.88	$734.90	$735.00