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	$169.46	6.827%	$181.029	$181.03	$181.05	$181.00
Purchase #2	$230.80	7.644%	$248.4424	$248.44	$248.45	$248.40
Purchase #3	$51.50	10.427%	$56.8699	$56.87	$56.85	$56.90
Purchase #4	$101.49	13.313%	$115.0014	$115.00	$115.00	$115.00
Purchase #5	$54.71	8.499%	$59.3598	$59.36	$59.35	$59.40
Purchase #6	$79.72	12.607%	$89.7703	$89.77	$89.75	$89.80
Purchase #7	$48.72	4.633%	$50.9772	$50.98	$51.00	$51.00
7 purchase totals =	$736.40		$801.4500	$801.45	$801.45	$801.50