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	$223.85	4.482%	$233.883	$233.88	$233.90	$233.90
Purchase #2	$31.67	5.623%	$33.4508	$33.45	$33.45	$33.50
Purchase #3	$247.91	8.551%	$269.1088	$269.11	$269.10	$269.10
Purchase #4	$108.30	10.198%	$119.3444	$119.34	$119.35	$119.30
Purchase #5	$51.60	6.319%	$54.8606	$54.86	$54.85	$54.90
Purchase #6	$209.89	11.319%	$233.6474	$233.65	$233.65	$233.60
Purchase #7	$135.60	7.447%	$145.6981	$145.70	$145.70	$145.70
7 purchase totals =	$1,008.82		$1,089.9931	$1,089.99	$1,090.00	$1,090.00