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	$155.47	10.522%	$171.8286	$171.83	$171.85	$171.80
Purchase #2	$89.29	9.549%	$97.8163	$97.82	$97.80	$97.80
Purchase #3	$49.49	10.113%	$54.4949	$54.49	$54.50	$54.50
Purchase #4	$216.28	10.143%	$238.2173	$238.22	$238.20	$238.20
Purchase #5	$164.93	5.757%	$174.425	$174.43	$174.45	$174.40
Purchase #6	$55.55	6.603%	$59.218	$59.22	$59.20	$59.20
Purchase #7	$52.55	6.147%	$55.7802	$55.78	$55.80	$55.80
7 purchase totals =	$783.56		$851.7803	$851.79	$851.80	$851.70