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	$25.65	12.826%	$28.9399	$28.94	$28.95	$28.90
Purchase #2	$218.90	6.560%	$233.2598	$233.26	$233.25	$233.30
Purchase #3	$29.75	10.401%	$32.8443	$32.84	$32.85	$32.80
Purchase #4	$125.90	3.311%	$130.0685	$130.07	$130.05	$130.10
Purchase #5	$89.65	5.568%	$94.6417	$94.64	$94.65	$94.60
Purchase #6	$12.71	8.767%	$13.8243	$13.82	$13.80	$13.80
Purchase #7	$248.45	5.638%	$262.4576	$262.46	$262.45	$262.50
7 purchase totals =	$751.01		$796.0361	$796.03	$796.00	$796.00