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	$133.36	7.491%	$143.35	$143.35	$143.35	$143.40
Purchase #2	$97.25	4.560%	$101.6846	$101.68	$101.70	$101.70
Purchase #3	$96.45	7.264%	$103.4561	$103.46	$103.45	$103.50
Purchase #4	$92.99	3.402%	$96.1535	$96.15	$96.15	$96.20
Purchase #5	$42.45	13.352%	$48.1179	$48.12	$48.10	$48.10
Purchase #6	$72.33	8.828%	$78.7153	$78.72	$78.70	$78.70
Purchase #7	$150.57	13.697%	$171.1936	$171.19	$171.20	$171.20
7 purchase totals =	$685.40		$742.6710	$742.67	$742.65	$742.80