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	$134.55	7.661%	$144.8579	$144.86	$144.85	$144.90
Purchase #2	$156.95	11.196%	$174.5221	$174.52	$174.50	$174.50
Purchase #3	$230.93	11.627%	$257.7802	$257.78	$257.80	$257.80
Purchase #4	$31.33	5.111%	$32.9313	$32.93	$32.95	$32.90
Purchase #5	$190.87	4.541%	$199.5374	$199.54	$199.55	$199.50
Purchase #6	$146.90	9.378%	$160.6763	$160.68	$160.70	$160.70
Purchase #7	$78.37	5.234%	$82.4719	$82.47	$82.45	$82.50
7 purchase totals =	$969.90		$1,052.7771	$1,052.78	$1,052.80	$1,052.80