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	$57.26	4.641%	$59.9174	$59.92	$59.90	$59.90
Purchase #2	$181.94	4.586%	$190.2838	$190.28	$190.30	$190.30
Purchase #3	$214.64	7.331%	$230.3753	$230.38	$230.40	$230.40
Purchase #4	$52.78	8.698%	$57.3708	$57.37	$57.35	$57.40
Purchase #5	$200.62	6.192%	$213.0424	$213.04	$213.05	$213.00
Purchase #6	$141.61	7.288%	$151.9305	$151.93	$151.95	$151.90
Purchase #7	$227.27	5.434%	$239.6199	$239.62	$239.60	$239.60
7 purchase totals =	$1,076.12		$1,142.5401	$1,142.54	$1,142.55	$1,142.50