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	$135.80	10.865%	$150.5547	$150.55	$150.55	$150.60
Purchase #2	$167.52	13.427%	$190.0129	$190.01	$190.00	$190.00
Purchase #3	$138.66	3.384%	$143.3523	$143.35	$143.35	$143.40
Purchase #4	$154.61	6.394%	$164.4958	$164.50	$164.50	$164.50
Purchase #5	$151.68	13.553%	$172.2372	$172.24	$172.25	$172.20
Purchase #6	$177.32	7.705%	$190.9825	$190.98	$191.00	$191.00
Purchase #7	$99.66	12.383%	$112.0009	$112.00	$112.00	$112.00
7 purchase totals =	$1,025.25		$1,123.6363	$1,123.63	$1,123.65	$1,123.70