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	$63.76	6.162%	$67.6889	$67.69	$67.70	$67.70
Purchase #2	$13.97	9.114%	$15.2432	$15.24	$15.25	$15.20
Purchase #3	$120.55	5.874%	$127.6311	$127.63	$127.65	$127.60
Purchase #4	$37.36	8.266%	$40.4482	$40.45	$40.45	$40.40
Purchase #5	$215.27	8.367%	$233.2816	$233.28	$233.30	$233.30
Purchase #6	$31.31	13.460%	$35.5243	$35.52	$35.50	$35.50
Purchase #7	$221.31	8.304%	$239.6876	$239.69	$239.70	$239.70
7 purchase totals =	$703.53		$759.5049	$759.50	$759.55	$759.40