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	$19.83	10.103%	$21.8334	$21.83	$21.85	$21.80
Purchase #2	$73.71	6.644%	$78.6073	$78.61	$78.60	$78.60
Purchase #3	$148.77	5.237%	$156.5611	$156.56	$156.55	$156.60
Purchase #4	$75.76	7.640%	$81.5481	$81.55	$81.55	$81.50
Purchase #5	$94.48	6.107%	$100.2499	$100.25	$100.25	$100.20
Purchase #6	$182.34	9.553%	$199.7589	$199.76	$199.75	$199.80
Purchase #7	$212.92	11.125%	$236.6074	$236.61	$236.60	$236.60
7 purchase totals =	$807.81		$875.1661	$875.17	$875.15	$875.10