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	$115.70	3.147%	$119.3411	$119.34	$119.35	$119.30
Purchase #2	$94.72	5.606%	$100.03	$100.03	$100.05	$100.00
Purchase #3	$105.28	9.658%	$115.4479	$115.45	$115.45	$115.40
Purchase #4	$160.47	7.503%	$172.5101	$172.51	$172.50	$172.50
Purchase #5	$42.75	7.597%	$45.9977	$46.00	$46.00	$46.00
Purchase #6	$130.36	10.365%	$143.8718	$143.87	$143.85	$143.90
Purchase #7	$111.64	11.475%	$124.4507	$124.45	$124.45	$124.50
7 purchase totals =	$760.92		$821.6493	$821.65	$821.65	$821.60