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	$158.45	6.309%	$168.4466	$168.45	$168.45	$168.40
Purchase #2	$167.62	10.607%	$185.3995	$185.40	$185.40	$185.40
Purchase #3	$139.63	12.340%	$156.8603	$156.86	$156.85	$156.90
Purchase #4	$160.86	8.484%	$174.5074	$174.51	$174.50	$174.50
Purchase #5	$157.79	7.853%	$170.1812	$170.18	$170.20	$170.20
Purchase #6	$60.39	9.445%	$66.0938	$66.09	$66.10	$66.10
Purchase #7	$75.76	9.728%	$83.1299	$83.13	$83.15	$83.10
7 purchase totals =	$920.50		$1,004.6187	$1,004.62	$1,004.65	$1,004.60