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	$79.32	10.816%	$87.8993	$87.90	$87.90	$87.90
Purchase #2	$168.61	4.387%	$176.0069	$176.01	$176.00	$176.00
Purchase #3	$50.47	6.697%	$53.85	$53.85	$53.85	$53.90
Purchase #4	$149.75	5.808%	$158.4475	$158.45	$158.45	$158.40
Purchase #5	$206.32	5.551%	$217.7728	$217.77	$217.75	$217.80
Purchase #6	$36.67	9.354%	$40.1001	$40.10	$40.10	$40.10
Purchase #7	$157.82	5.426%	$166.3833	$166.38	$166.40	$166.40
7 purchase totals =	$848.96		$900.4599	$900.46	$900.45	$900.50