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	$61.60	4.359%	$64.2851	$64.29	$64.30	$64.30
Purchase #2	$132.89	3.375%	$137.375	$137.38	$137.40	$137.40
Purchase #3	$190.82	12.836%	$215.3137	$215.31	$215.30	$215.30
Purchase #4	$113.67	9.400%	$124.355	$124.36	$124.35	$124.40
Purchase #5	$81.26	10.682%	$89.9402	$89.94	$89.95	$89.90
Purchase #6	$33.45	10.535%	$36.974	$36.97	$36.95	$37.00
Purchase #7	$56.60	3.296%	$58.4655	$58.47	$58.45	$58.50
7 purchase totals =	$670.29		$726.7085	$726.72	$726.70	$726.80