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	$66.92	7.211%	$71.7456	$71.75	$71.75	$71.70
Purchase #2	$58.57	4.530%	$61.2232	$61.22	$61.20	$61.20
Purchase #3	$105.27	13.507%	$119.4888	$119.49	$119.50	$119.50
Purchase #4	$193.90	3.406%	$200.5042	$200.50	$200.50	$200.50
Purchase #5	$223.86	3.161%	$230.9362	$230.94	$230.95	$230.90
Purchase #6	$239.47	4.746%	$250.8352	$250.84	$250.85	$250.80
Purchase #7	$58.59	11.446%	$65.2962	$65.30	$65.30	$65.30
7 purchase totals =	$946.58		$1,000.0294	$1,000.04	$1,000.05	$999.90