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	$90.75	5.154%	$95.4273	$95.43	$95.45	$95.40
Purchase #2	$168.81	5.730%	$178.4828	$178.48	$178.50	$178.50
Purchase #3	$157.90	12.754%	$178.0386	$178.04	$178.05	$178.00
Purchase #4	$84.52	6.374%	$89.9073	$89.91	$89.90	$89.90
Purchase #5	$237.64	6.316%	$252.6493	$252.65	$252.65	$252.60
Purchase #6	$119.29	7.543%	$128.288	$128.29	$128.30	$128.30
Purchase #7	$156.48	4.152%	$162.977	$162.98	$163.00	$163.00
7 purchase totals =	$1,015.39		$1,085.7703	$1,085.78	$1,085.85	$1,085.70