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	$147.35	6.319%	$156.661	$156.66	$156.65	$156.70
Purchase #2	$65.64	7.334%	$70.454	$70.45	$70.45	$70.50
Purchase #3	$119.54	7.833%	$128.9036	$128.90	$128.90	$128.90
Purchase #4	$16.50	6.141%	$17.5133	$17.51	$17.50	$17.50
Purchase #5	$56.71	10.300%	$62.5511	$62.55	$62.55	$62.60
Purchase #6	$143.40	6.549%	$152.7913	$152.79	$152.80	$152.80
Purchase #7	$231.42	6.527%	$246.5248	$246.52	$246.50	$246.50
7 purchase totals =	$780.56		$835.3991	$835.38	$835.35	$835.50