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	$82.56	4.372%	$86.1695	$86.17	$86.15	$86.20
Purchase #2	$228.66	11.139%	$254.1304	$254.13	$254.15	$254.10
Purchase #3	$29.42	9.190%	$32.1237	$32.12	$32.10	$32.10
Purchase #4	$225.37	5.123%	$236.9157	$236.92	$236.90	$236.90
Purchase #5	$63.96	12.662%	$72.0586	$72.06	$72.05	$72.10
Purchase #6	$31.83	7.207%	$34.124	$34.12	$34.10	$34.10
Purchase #7	$225.65	13.226%	$255.4945	$255.49	$255.50	$255.50
7 purchase totals =	$887.45		$971.0164	$971.01	$970.95	$971.00