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	$48.83	8.541%	$53.0006	$53.00	$53.00	$53.00
Purchase #2	$45.32	6.569%	$48.2971	$48.30	$48.30	$48.30
Purchase #3	$233.76	10.393%	$258.0547	$258.05	$258.05	$258.10
Purchase #4	$131.57	7.510%	$141.4509	$141.45	$141.45	$141.50
Purchase #5	$31.54	12.471%	$35.4734	$35.47	$35.45	$35.50
Purchase #6	$98.66	6.457%	$105.0305	$105.03	$105.05	$105.00
Purchase #7	$119.64	11.389%	$133.2658	$133.27	$133.25	$133.30
7 purchase totals =	$709.32		$774.5730	$774.57	$774.55	$774.70