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	$76.30	8.493%	$82.7802	$82.78	$82.80	$82.80
Purchase #2	$144.73	9.264%	$158.1378	$158.14	$158.15	$158.10
Purchase #3	$200.68	12.507%	$225.779	$225.78	$225.80	$225.80
Purchase #4	$130.64	10.424%	$144.2579	$144.26	$144.25	$144.30
Purchase #5	$93.81	4.268%	$97.8138	$97.81	$97.80	$97.80
Purchase #6	$160.75	6.611%	$171.3772	$171.38	$171.40	$171.40
Purchase #7	$66.96	7.780%	$72.1695	$72.17	$72.15	$72.20
7 purchase totals =	$873.87		$952.3154	$952.32	$952.35	$952.40